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Assessing ChatGPT’s Performance in Analyzing Students’ Sentiments: A Case Study in Course Feedback (2024)

Sarda, Akshay Rajkumar

The emergence of large language models (LLMs) like ChatGPT has impacted fields such as education, transforming natural language processing (NLP) tasks like sentiment analysis. Transformers form the foundation of LLMs, with BERT, XLNet, and GPT as key examples. ChatGPT, developed by OpenAI, is a state-of-the-art model and its ability in natural language tasks makes it a potential tool in sentiment analysis. This thesis reviews current sentiment analysis methods and examines ChatGPT’s ability to analyze sentiments across three labels (Negative, Neutral, Positive) and five labels (Very Negative, Negative, Neutral, Positive, Very Positive) on a dataset of student course reviews. Its performance is compared with fine tuned state-of-the-art models like BERT, XLNet, bart-large-mnli, and RoBERTa-large-mnli using quantitative metrics. With the help of 7 prompting techniques which are ways to instruct ChatGPT, this work also analyzed how well it understands complex linguistic nuances in the given texts using qualitative metrics. BERT and XLNet outperform ChatGPT mainly due to their bidirectional nature, which allows them to understand the full context of a sentence, not just left to right. This, combined with fine-tuning, helps them capture patterns and nuances better. ChatGPT, as a general purpose, open-domain model, processes text unidirectionally, which can limit its context understanding. Despite this, ChatGPT performed comparably to XLNet and BERT in three-label scenarios and outperformed others. Fine-tuned models excelled in five label cases. Moreover, it has shown impressive knowledge of the language. Chain-of-Thought (CoT) was the most effective technique for prompting with step by step instructions. ChatGPT showed promising performance in correctness, consistency, relevance, and robustness, except for detecting Irony. As education evolves with diverse learning environments, effective feedback analysis becomes increasingly valuable. Addressing ChatGPT’s limitations and leveraging its strengths could enhance personalized learning through better sentiment analysis.

Exploring Academic Perspectives: Sentiments and Discourse on ChatGPT Adoption in Higher Education (2024)

Gopal, Yashwanth

Artificial intelligence (AI) is becoming more widely used in a number of industries, including in the field of education. Applications of artificial intelligence (AI) are becoming crucial for schools and universities, whether for automated evaluation, smart educational systems, individualized learning, or staff support. ChatGPT, anAI-based chatbot, offers coherent and helpful replies based on analyzing large volumes of data. Integrating ChatGPT, a sophisticated Natural Language Processing (NLP) tool developed by OpenAI, into higher education has sparked significant interest and debate. Since the technology is already adapted by many students and teachers, this study delves into analyzing the sentiments expressed on university websites regarding ChatGPT integration into education by creating a comprehensive sentiment analysis framework using Hierarchical Residual RSigELU Attention Network (HR-RAN). The proposed framework addresses several challenges in sentiment analysis, such as capturing fine-grained sentiment nuances, including contextual information, and handling complex language expressions in university review data. The methodology involves several steps, including data collection from various educational websites, blogs, and news platforms. The data is preprocessed to handle emoticons, URLs, and tags and then, detect and remove sarcastic text using the eXtreme Learning Hyperband Network (XLHN). Sentences are then grouped based on similarity and topics are modeled using the Non-negative Term-Document Matrix Factorization (NTDMF) approach. Features, such as lexico-semantic, lexico structural, and numerical features are extracted. Dependency parsing and coreference resolution are performed to analyze grammatical structures and understand semantic relationships. Word embedding uses the Word2Vec model to capture semantic relationships between words. The preprocessed text and extracted features are inputted into the HR-RAN classifier to categorize sentiments as positive, negative, or neutral. The sentiment analysis results indicate that 74.8% of the sentiments towards ChatGPT in higher education are neutral, 21.5% are positive, and only 3.7% are negative. This suggests a predominant neutrality among users, with a significant portion expressing positive views and a very small percentage holding negative opinions. Additionally, the analysis reveals regional variations, with Canada showing the highest number of sentiments, predominantly neutral, followed by Germany, the UK, and the USA. The sentiment analysis results are evaluated based on various metrics, such as accuracy, precision, recall, F-measure, and specificity. Results indicate that the proposed framework outperforms conventional sentiment analysis models. The HR-RAN technique achieved a precision of 98.98%, recall of 99.23%, F-measure of 99.10%, accuracy of 98.88%, and specificity of 98.31%. Additionally, word clouds are generated to visually represent the most common terms within positive, neutral, and negative sentiments, providing a clear and immediate understanding of the key themes in the data. These findings can inform educators, administrators, and developers about the benefits and challenges of integrating ChatGPT into educational settings, guiding improvements in educational practices and AI tool development.

Applications for Symbol Elimination in Combination with Hierarchical Reasoning (2024)

Peuter, Dennis

The goal of this PhD thesis is to investigate possibilities of using symbol elimination for solving problems over complex theories and analyze the applicability of such uniform approaches in different areas of application, such as verification, knowledge representation and graph theory. In the thesis we propose an approach to symbol elimination in complex theories that follows the general idea of combining hierarchical reasoning with symbol elimination in standard theories. We analyze how this general approach can be specialized and used in different areas of application. In the verification of parametric systems it is important to prove that certain safety properties hold. This can be done by showing that a property is an inductive invariant of the system, i.e. it holds in the initial state of the system and is invariant under updates of the system. Sometimes this is not the case for the condition itself, but for a stronger condition it is. In this thesis we propose a method for goal-directed invariant strengthening. In knowledge representation we often have to deal with huge ontologies. Combining two ontologies usually leads to new consequences, some of which may be false or undesired. We are interested in finding explanations for such unwanted consequences. For this we propose a method for computing interpolants in the description logics EL and EL⁺, based on a translation to the theory of semilattices with monotone operators and a certain form of interpolation in this theory. In wireless network theory one often deals with classes of geometric graphs in which the existence or non-existence of an edge between two vertices in a graph relies on properties on their distances to other nodes. One possibility to prove properties of those graphs or to analyze relations between the graph classes is to prove or disprove that one graph class is contained in the other. In this thesis we propose a method for checking inclusions between geometric graph classes.

Decentralized Fair Data Exchange with Minimal Mutual Trust using Distributed Ledgers (2024)

Lohr, Matthias

In international business relationships, such as international railway operations, large amounts of data can be exchanged among the parties involved. For the exchange of such data, a limited risk of being cheated by another party, e.g., by being provided with fake data, as well as reasonable cost and a foreseeable benefit, is expected. As the exchanged data can be used to make critical business decisions, there is a high incentive for one party to manipulate the data in its favor. To prevent this type of manipulation, mechanisms exist to ensure the integrity and authenticity of the data. In combination with a fair exchange protocol, it can be ensured that the integrity and authenticity of this data is maintained even when it is exchanged with another party. At the same time, such a protocol ensures that the exchange of data only takes place in conjunction with the agreed compensation, such as a payment, and that the payment is only made if the integrity and authenticity of the data is ensured as previously agreed. However, in order to be able to guarantee fairness, a fair exchange protocol must involve a trusted third party. To avoid fraud by a single centralized party acting as a trusted third party, current research proposes decentralizing the trusted third party, e.g., by using a distributed ledger based fair exchange protocol. However, for assessing the fairness of such an exchange, state-of-the-art approaches neglect costs arising for the parties conducting the fair exchange. This can result in a violation of the outlined expectation of reasonable cost, especially when distributed ledgers are involved, which are typically associated with non-negligible costs. Furthermore, the performance of typical distributed ledger-based fair exchange protocols is limited, posing an obstacle to widespread adoption. To overcome the challenges, in this thesis, we introduce the foundation for a data exchange platform allowing for a fully decentralized fair data exchange with reasonable cost and performance. As a theoretical foundation, we introduce the concept of cost fairness, which considers cost for the fairness assessment by requesting that a party following the fair exchange protocol never suffers any unilateral disadvantages. We prove that cost fairness cannot be achieved using typical public distributed ledgers but requires customized distributed ledger instances, which usually lack complete decentralization. However, we show that the highest unilateral cost are caused by a grieving attack. To allow fair data exchanges to be conducted with reasonable cost and performance, we introduce FairSCE, a distributed ledger-based fair exchange protocol using distributed ledger state channels and incorporating a mechanism to protect against grieving attacks, reducing the possible unilateral cost that have to be covered to a minimum. Based on our evaluation of FairSCE, the worst-case cost for data exchange, even in the presence of malicious parties, is known, which allows an estimate of the possible benefit and, thus, the preliminary estimate of economic utility. Furthermore, to allow for an unambiguous assessment of the correct data being transferred while still allowing for sensitive parts of the data to be masked, we introduce an approach for the hashing of hierarchically structured data, which can be used to ensure integrity and authenticity of the data being transferred.

Technical and Methodological Improvements to Mining Software Repositories (2024)

Härtel, Johannes

Empirical studies in software engineering use software repositories as data sources to understand software development. Repository data is either used to answer questions that guide the decision-making in the software development, or to provide tools that help with practical aspects of developers’ everyday work. Studies are classified into the field of Empirical Software Engineering (ESE), and more specifically into Mining Software Repositories (MSR). Studies working with repository data often focus on their results. Results are statements or tools, derived from the data, that help with practical aspects of software development. This thesis focuses on the methods and high order methods used to produce such results. In particular, we focus on incremental methods to scale the processing of repositories, declarative methods to compose a heterogeneous analysis, and high order methods used to reason about threats to methods operating on repositories. We summarize this as technical and methodological improvements. We contribute the improvements to methods and high-order methods in the context of MSR/ESE to produce future empirical results more effectively. We contribute the following improvements. We propose a method to improve the scalability of functions that abstract over repositories with high revision count in a theoretically founded way. We use insights on abstract algebra and program incrementalization to define a core interface of highorder functions that compute scalable static abstractions of a repository with many revisions. We evaluate the scalability of our method by benchmarks, comparing a prototype with available competitors in MSR/ESE. We propose a method to improve the definition of functions that abstract over a repository with a heterogeneous technology stack, by using concepts from declarative logic programming and combining them with ideas on megamodeling and linguistic architecture. We reproduce existing ideas on declarative logic programming with languages close to Datalog, coming from architecture recovery, source code querying, and static program analysis, and transfer them from the analysis of a homogeneous to a heterogeneous technology stack. We provide a prove-of-concept of such method in a case study. We propose a high-order method to improve the disambiguation of threats to methods used in MSR/ESE. We focus on a better disambiguation of threats, operationalizing reasoning about them, and making the implications to a valid data analysis methodology explicit, by using simulations. We encourage researchers to accomplish their work by implementing ‘fake’ simulations of their MSR/ESE scenarios, to operationalize relevant insights about alternative plausible results, negative results, potential threats and the used data analysis methodologies. We prove that such way of simulation based testing contributes to the disambiguation of threats in published MSR/ESE research.

Wireless communication on the factory floor supporting agile production (2023)

Lyczkowski, Eike

The trends of industry 4.0 and the further enhancements toward an ever changing factory lead to more mobility and flexibility on the factory floor. With that higher need of mobility and flexibility the requirements on wireless communication rise. A key requirement in that setting is the demand for wireless Ultra-Reliability and Low Latency Communication (URLLC). Example use cases therefore are cooperative Automated Guided Vehicles (AGVs) and mobile robotics in general. Working along that setting this thesis provides insights regarding the whole network stack. Thereby, the focus is always on industrial applications. Starting on the physical layer, extensive measurements from 2 GHz to 6 GHz on the factory floor are performed. The raw data is published and analyzed. Based on that data an improved Saleh-Valenzuela (SV) model is provided. As ad-hoc networks are highly depended onnode mobility, the mobility of AGVs is modeled. Additionally, Nodal Encounter Patterns (NEPs) are recorded and analyzed. A method to record NEP is illustrated. The performance by means of latency and reliability are key parameters from an application perspective. Thus, measurements of those two parameters in factory environments are performed using Wireless Local Area Network (WLAN) (IEEE 802.11n), private Long Term Evolution (pLTE) and 5G. This showed auto-correlated latency values. Hence, a method to construct confidence intervals based on auto-correlated data containing rare events is developed. Subsequently, four performance improvements for wireless networks on the factory floor are proposed. Of those optimization three cover ad-hoc networks, two deal with safety relevant communication, one orchestrates the usage of two orthogonal networks and lastly one optimizes the usage of information within cellular networks. Finally, this thesis is concluded by an outlook toward open research questions. This includes open questions remaining in the context of industry 4.0 and further the ones around 6G. Along the research topics of 6G the two most relevant topics concern the ideas of a network of networks and overcoming best-effort IP.

Practices, Networks and Success in Creative Careers: Study of Inequalities using Large-scale Digital Behavioural Data (2023)

Jadidi, Mohsen

In the last decade, policy-makers around the world have turned their attention toward the creative industry as the economic engine and significant driver of employments. Yet, the literature suggests that creative workers are one of the most vulnerable work-forces of today’s economy. Because of the highly deregulated and highly individuated environment, failure or success are believed to be the byproduct of individual ability and commitment, rather than a structural or collective issue. This thesis taps into the temporal, spatial, and social resolution of digital behavioural data to show that there are indeed structural and historical issues that impact individuals’ and groups’ careers. To this end, this thesis offers a computational social science research framework that brings together the decades-long theoretical and empirical knowledge of inequality studies, and computational methods that deal with the complexity and scale of digital data. By taking music industry and science as use cases, this thesis starts off by proposing a novel gender detection method that exploits image search and face-detection methods. By analysing the collaboration patterns and citation networks of male and female computer scientists, it sheds lights on some of the historical biases and disadvantages that women face in their scientific career. In particular, the relation of scientific success and gender-specific collaboration patterns is assessed. To elaborate further on the temporal aspect of inequalities in scientific careers, this thesis compares the degree of vertical and horizontal inequalities among the cohorts of scientists that started their career at different point in time. Furthermore, the structural inequality in music industry is assessed by analyzing the social and cultural relations that breed from live performances and musics releases. The findings hint toward the importance of community belonging at different stages of artists’ careers. This thesis also quantifies some of the underlying mechanisms and processes of inequality, such as the Matthew Effect and the Hipster Paradox, in creative careers. Finally, this thesis argues that online platforms such as Wikipedia could reflect and amplify the existing biases.

Nutzungsakzeptanz von digitalen Werkzeugen in den Geisteswissenschaften (2022)

Simon, Tobias

Currently, there are a variety of digital tools in the humanities, such as annotation, visualization, or analysis software, which support researchers in their work and offer them new opportunities to address different research questions. However, the use of these tools falls far short of expectations. In this thesis, twelve improvement measures are developed within the framework of a design science theory to counteract the lack of usage acceptance. By implementing the developed design science theory, software developers can increase the acceptance of their digital tools in the humanities context.

Knowledge engineering for software languages and software technologies (2022)

Heinz, Marcel

For software engineers, conceptually understanding the tools they are using in the context of their projects is a daily challenge and a prerequisite for complex tasks. Textual explanations and code examples serve as knowledge resources for understanding software languages and software technologies. This thesis describes research on integrating and interconnecting existing knowledge resources, which can then be used to assist with understanding and comparing software languages and software technologies on a conceptual level. We consider the following broad research questions that we later refine: What knowledge resources can be systematically reused for recovering structured knowledge and how? What vocabulary already exists in literature that is used to express conceptual knowledge? How can we reuse the online encyclopedia Wikipedia? How can we detect and report on instances of technology usage? How can we assure reproducibility as the central quality factor of any construction process for knowledge artifacts? As qualitative research, we describe methodologies to recover knowledge resources by i.) systematically studying literature, ii.) mining Wikipedia, iii.) mining available textual explanations and code examples of technology usage. The theoretical findings are backed by case studies. As research contributions, we have recovered i.) a reference semantics of vocabulary for describing software technology usage with an emphasis on software languages, ii.) an annotated corpus of Wikipedia articles on software languages, iii.) insights into technology usage on GitHub with regard to a catalog of pattern and iv.) megamodels of technology usage that are interconnected with existing textual explanations and code examples.

Emotion and Sentiment Detection in Unstructured Social Data (2022)

AlGhalibi, Maha

Social media provides a powerful way for people to share opinions and sentiments about a specific topic, allowing others to benefit from these thoughts and feelings. This procedure generates a huge amount of unstructured data, such as texts, images, and references that are constantly increasing through daily comments to related discussions. However, the vast amount of unstructured data presents risks to the information-extraction process, and so decision making becomes highly challenging. This is because data overload may cause the loss of useful data due to its inappropriate presentation and its accumulation. To this extent, this thesis contributed to the field of analyzing and detecting feelings in images and texts. And that by extracting the feelings and opinions hidden in a huge collection of image data and texts on social networks After that, these feelings are classified into positive, negative, or neutral, according to the features of the classified data. The process of extracting these feelings greatly helps in decision-making processes on various topics as will be explained in the first chapter of the thesis. A system has been built that can classify the feelings inherent in the images and texts on social media sites, such as people’s opinions about products and companies, personal posts, and general messages. This thesis begins by introducing a new method of reducing the dimension of text data based on data-mining approaches and then examines the sentiment based on neural and deep neural network classification algorithms. Subsequently, in contrast to sentiment analysis research in text datasets, we examine sentiment expression and polarity classification within and across image datasets by building deep neural networks based on the attention mechanism.

Proactive Content Placement in Information-Centric Connected Vehicle Environments (2021)

Grewe, Dennis

Connected vehicles will have a tremendous impact on tomorrow’s mobility solutions. Such systems will heavily rely on information delivery in time to ensure the functional reliability, security and safety. However, the host-centric communication model of today’s networks questions efficient data dissemination in a scale, especially in networks characterized by a high degree of mobility. The Information-Centric Networking (ICN) paradigm has evolved as a promising candidate for the next generation of network architectures. Based on a loosely coupled communication model, the in-network processing and caching capabilities of ICNs are promising to solve the challenges set by connected vehicular systems. In such networks, a special class of caching strategies which take action by placing a consumer’s anticipated content actively at the right network nodes in time are promising to reduce the data delivery time. This thesis contributes to the research in active placement strategies in information-centric and computation-centric vehicle networks for providing dynamic access to content and computation results. By analyzing different vehicular applications and their requirements, novel caching strategies are developed in order to reduce the time of content retrieval. The caching strategies are compared and evaluated against the state-of-the-art in both extensive simulations as well as real world deployments. The results are showing performance improvements by increasing the content retrieval (availability of specific data increased up to 35% compared to state-of-the-art caching strategies), and reducing the delivery times (roughly double the number of data retrieval from neighboring nodes). However, storing content actively in connected vehicle networks raises questions regarding security and privacy. In the second part of the thesis, an access control framework for information-centric connected vehicles is presented. Finally, open security issues and research directions in executing computations at the edge of connected vehicle networks are presented.

Latency Reduction for Real-Time Rendering and its Application to VR Training Scenarios (2021)

Lochmann, Gerrit

Virtual reality is a growing field of interest as it provides a particular intuitive way of user-interaction. However, there are still open technical issues regarding latency — the delay between interaction and display reaction — and the trade-off between visual quality and frame-rate of real-time graphics, especially when taking visual effects like specular and semi-transparent surfaces and volumes into account. One solution, a distributed rendering setup, is presented in this thesis, in which the image synthesis is divided into an accurate but costly physically based rendering thread with a low refresh rate and a fast reprojection thread to remain a responsive interactivity with a high frame-rate. Two novel reprojection techniques are proposed that cover reflections and refractions produced by surface ray-tracing as well as volumetric light transport generated by volume ray-marching. The introduced setup can enhance the VR experience within several domains. In this thesis, three innovative training applications have been realized to investigate the added value of virtual reality to the three learning stages of observation, interaction and collaboration. For each stage an interdisciplinary curriculum, currently taught with traditional media, was transferred to a VR setting in order to investigate how virtual reality is capable of providing a natural, flexible and efficient learning environment

Nuclear Potential Clustering of Data (2020)

Tonkova, Vyara

Initial goal of the current dissertation was the determination of image-based biomarkers sensitive for neurodegenerative processes in the human brain. One such process is the demyelination of neural cells characteristic for Multiple sclerosis (MS) - the most common neurological disease in young adults for which there is no cure yet. Conventional MRI techniques are very effective in localizing areas of brain tissue damage and are thus a reliable tool for the initial MS diagnosis. However, a mismatch between the clinical fndings and the visualized areas of damage is observed, which renders the use of the standard MRI diffcult for the objective disease monitoring and therapy evaluation. To address this problem, a novel algorithm for the fast mapping of myelin water content using standard multiecho gradient echo acquisitions of the human brain is developed in the current work. The method extents a previously published approach for the simultaneous measurement of brain T1, T∗ 2 and total water content. Employing the multiexponential T∗ 2 decay signal of myelinated tissue, myelin water content is measured based on the quantifcation of two water pools (myelin water and rest) with different relaxation times. Whole brain in vivo myelin water content maps are acquired in 10 healthy controls and one subject with MS. The in vivo results obtained are consistent with previous reports. The acquired quantitative data have a high potential in the context of MS. However, the parameters estimated in a multiparametric acquisition are correlated and constitute therefore an ill-posed, nontrivial data analysis problem. Motivated by this specific problem, a new data clustering approach is developed called Nuclear Potential Clustering, NPC. It is suitable for the explorative analysis of arbitrary dimensional and possibly correlated data without a priori assumptions about its structure. The developed algorithm is based on a concept adapted from nuclear physics. To partition the data, the dynamic behavior of electrically even charged nucleons interacting in a d-dimensional feature space is modeled. An adaptive nuclear potential, comprised of a short-range attractive (Strong interaction) and a long-range repulsive term (Coulomb potential), is assigned to each data point. Thus, nucleons that are densely distributed in space fuse to build nuclei (clusters), whereas single point clusters are repelled (noise). The algorithm is optimized and tested in an extensive study with a series of synthetic datasets as well as the Iris data. The results show that it can robustly identify clusters even when complex configurations and noise are present. Finally, to address the initial goal, quantitative MRI data of 42 patients are analyzed employing NPC. A series of experiments with different sets of image-based features show a consistent grouping tendency: younger patients with low disease grade are recognized as cohesive clusters, while those of higher age and impairment are recognized as outliers. This allows for the definition of a reference region in a feature space associated with phenotypic data. Tracking of the individual's positions therein can disclose patients at risk and be employed for therapy evaluation.

Weiterentwicklung und Implementierung des Projekts "Instahub" für die Sekundarstufe I mit dem Themenschwerpunkt Datenschutz (2019)

Savelsberg, Jan

Eine didaktisch-methodische Ausarbeitung einer Unterrichtsreihe zur Online-Plattform InstaHub mit dem Themenschwerpunkt Datenschutz. Die Unterrichtsreihe ist für die Klassenstufe 5-6 (und höher) eines Gymnasiums geeignet. Weiterhin werden Anregungen für Datenschutz im Unterricht gegeben.

A rule-based approach for the automatic extraction of Mega Models (2018)

Rüther, Frederik

Modern software projects are composed of several software languages, software technologies and different kind of artifacts. Therefore, the understanding of the software project at hand, including the semantic links between the different parts, becomes a difficult challenge for a developer. One approach to attack this issue is to document the software project with the help of a linguistic architecture. This kind of architecture can be described with the help of the MegaL ontology. A remaining challenge is the creation of it since it requires different kind of skills. Therefore, this paper proposes an approach for the automatic extraction of a linguistic architecture. The open source framework Apache Jena, which is focusing on semantic web technologies like RDF and OWL, is used to define custom rules that are capable to infer new knowledge based on the defined or already extracted RDF triples. The complete approach is tested in a case study on ten different open source projects. The aim of the case study is to extract a linguistic architecture that is describing the use of Hibernate in the selected projects. In the end, the result is evaluated with the help of different metrics. The evaluation is performed with the help of an internal and external approach.

Software chrestomathy as a knowledge-driven research infrastructure for software engineering (2018)

Varanovich, Andrei

The term “Software Chrestomaty” is defined as a collection of software systems meant to be useful in learning about or gaining insight into software languages, software technologies, software concepts, programming, and software engineering. 101companies software chrestomathy is a community project with the attributes of a Research 2.0 infrastructure for various stakeholders in software languages and technology communities. The core of 101companies combines a semantic wiki and confederated open source repositories. We designed and developed an integrated ontology-based knowledge base about software languages and technologies. The knowledge is created by the community of contributors and supported with a running example and structured documentation. The complete ecosystem is exposed by using Linked Data principles and equipped with the additional metadata about individual artifacts. Within the context of software chrestomathy we explored a new type of software architecture – linguistic architecture that is targeted on the language and technology relationships within a software product and based on the megamodels. Our approach to documentation of the software systems is highly structured and makes use of the concepts of the newly developed megamodeling language MegaL. We “connect” an emerging ontology with the megamodeling artifacts to raise the cognitive value of the linguistic architecture.

Modellbasierte Poseschätzung in monokularen Aufnahmen unter Verwendung geometrischer Modelle (2017)

Wirtz, Stefan

Die Forschung im Bereich der modellbasierten Objekterkennung und Objektlokalisierung hat eine vielversprechende Zukunft, insbesondere die Gebäudeerkennung bietet vielfaltige Anwendungsmöglichkeiten. Die Bestimmung der Position und der Orientierung des Beobachters relativ zu einem Gebäude ist ein zentraler Bestandteil der Gebäudeerkennung. Kern dieser Arbeit ist es, ein System zur modellbasierten Poseschätzung zu entwickeln, das unabhängig von der Anwendungsdomäne agiert. Als Anwendungsdomäne wird die modellbasierte Poseschätzung bei Gebäudeaufnahmen gewählt. Vorbereitend für die Poseschätzung bei Gebäudeaufnahmen wird die modellbasierte Erkennung von Dominosteinen und Pokerkarten realisiert. Eine anwendungsunabhängige Kontrollstrategie interpretiert anwendungsspezifische Modelle, um diese im Bild sowohl zu lokalisieren als auch die Pose mit Hilfe dieser Modelle zu bestimmen. Es wird explizit repräsentiertes Modellwissen verwendet, sodass Modellbestandteilen Bildmerkmale zugeordnet werden können. Diese Korrespondenzen ermöglichen die Kamerapose aus einer monokularen Aufnahme zurückzugewinnen. Das Verfahren ist unabhängig vom Anwendungsfall und kann auch mit Modellen anderer rigider Objekte umgehen, falls diese der definierten Modellrepräsentation entsprechen. Die Bestimmung der Pose eines Modells aus einem einzigen Bild, das Störungen und Verdeckungen aufweisen kann, erfordert einen systematischen Vergleich des Modells mit Bilddaten. Quantitative und qualitative Evaluationen belegen die Genauigkeit der bestimmten Gebäudeposen. In dieser Arbeit wird zudem ein halbautomatisches Verfahren zur Generierung eines Gebäudemodells vorgestellt. Das verwendete Gebäudemodell, das sowohl semantisches als auch geometrisches Wissen beinhaltet, den Aufgaben der Objekterkennung und Poseschätzung genügt und sich dennoch an den bestehenden Normen orientiert, ist Voraussetzung für das Poseschätzverfahren. Leitgedanke der Repräsentationsform des Modells ist, dass sie für Menschen interpretierbar bleibt. Es wurde ein halbautomatischer Ansatz gewählt, da die automatische Umsetzung dieses Verfahrens schwer die nötige Präzision erzielen kann. Das entwickelte Verfahren erreicht zum einen die nötige Präzision zur Poseschätzung und reduziert zum anderen die Nutzerinteraktionen auf ein Minimum. Eine qualitative Evaluation belegt die erzielte Präzision bei der Generierung des Gebäudemodells.

Fehlerrate von lokalen Routingverfahren in teilplanarisierten Graphen unter Verwendung des Log-Normal-Shadowing-Modells (2017)

Bremer, Nicole

Skalierbarkeit und garantierte Ausliererung sind essentielle Eigenschaften eines jeden Routingalgorithmus. Beides bietet bei drahtlosen Ad-hoc Netzwerken die Kombination aus Greedy- und Face- Routing, sofern ein planarer Graph zur Verfügung steht. Doch gerade die fehlerfreie Planarisierung bereitet bei realistischen Netzwerken Schwierigkeiten. Daher soll mit dieser Arbeit die Frage beantwortet werden, zu welcher Fehlerrate es führt, wenn der Graph lediglich mit lokalen Methoden teilplanarisiert wird. Dazu wurde eine Simulationsumgebung geschaffen, um unter Anwendung des Log-Normal-Shadowing-Modells zufällige Konnektivitätsgraphen zu generieren. Diese wurden anschließend durch zwei unterschiedliche, lokale Strategien teilplanarisiert. Es wurden neun verschiedene Settings definiert, die sich aus drei unterschiedlichen Graphendichten und drei unterschiedlichen Werten für den Sigmaparameter des Log-Normal-Shadowing-Modells ergeben. Für jedes Setting wurde in 2000 Simulationsdurchläufen das Verhalten von Greedy-, Face- und kombiniertem Greedy-Face-Routing untersucht und ausgewertet. Zum Abschluss wurden die Ergebnisse dieser Simulation bewertet und diskutiert.

Entwicklung und Konzeption eines E-Learning Kurses für Programmieranfänger (2017)

Kramer, Kasjen

E-Learning Anwendungen sind heutzutage im Trend. Jedoch nicht nur aus diesem Grund sind sie vom großen Interesse. Im Vordergrund steht ihr didaktisches Konzept. Heutzutage ist es technisch möglich, die Teilnehmer interaktiv in einen E- Learning Kurs einzubinden. Die Lernschritte können durch die Anwendung kontrolliert werden. Im Gegensatz zu einer Vorlesung, kann die Theorie direkt mit der Praxis verknüpft werden. Das Ziel der Arbeit ist die Erstellung eines Konzeptes und die Entwicklung eines Prototypen einer interaktiven Entwicklungsumgebung von Java für Programmieranfänger. In dieser Arbeit wurden aktuelle E-Learning Plattformen zu Java analysiert. Aus den gewonnen Erkenntnissen wurde ein Konzept für eine E-Learningplattform entwickelt. Dieses Konzept wurde erfolgreich als Prototyp implementiert. Für die Implementation wurden bewährte Technologien, wie das Django-Framework und das Javascript-Framework Vue.js eingesetzt. Der Kurs wurde von neun Teilnehmern getestet. Zusätzlich wurde eine Umfrage zu der Kursanwendung durchgeführt. Das Testergebnis bestätigt, dass die Teilnehmer den Kurs bestanden haben.

Semantics4J - Programming language integrated queries and types (2017)

Hartenfels, Carsten

Using semantic data from general-purpose programming languages does not provide the unified experience one would want for such an application. Static error checking is lacking, especially with regards to static typing of the data. Based on the previous work of λ-DL, which integrates semantic queries and concepts as types into a typed λ-calculus, this work takes its ideas a step further to meld them into a real-world programming language. This thesis explores how λ-DL's features can be extended and integrated into an existing language, researches an appropriate extension mechanism and produces Semantics4J, a JastAdd-based Java language semantic data extension for type-safe OWL programming, together with examples of its usage.

Real-time sensor-based motion capture system for virtual reality (2017)

Christ, Vera

Motion capture refers to the process of capturing, processing and trans- lating real motions onto a 3D model. Not only in the movie and gaming industries, motion capture creates an indispensable realism of human and animal movement. Also in the context of robotics, medical movement therapy, as well as in AR and VR, motion capture is used extensively. In addition to the well established optical processes, especially in the last three areas, alternative systems based on inertial navigation (IMUs) are being used in-creasingly, because they do not rely on external cameras and thus limit the area of movement considerably less. Fast evolving technical progress in the manufacturing of such IMUs allows building small sensors, wearable on the body which can transfer movements to a computer. The development of applying inertial systems to a motion capture context, however, is still at an early state. Problems like drift can currently only be minimized by adding additional hardware for correcting the read data. In the following master thesis an IMU based motion capture system is designed and constructed. This contains the assembly of the hardware components as well as processing of the received movement data on the software side and their application to a 3D model.

OSS vulnerabilities through islands of knowledge (2017)

Brack, Marco

This thesis proposes the use of MSR (Mining Software Repositories) techniques to identify software developers with exclusive expertise about specific APIs and programming domains in software repositories. A pilot Tool for finding such “Islands of Knowledge” in Node.js projects is presented and applied in a case study to the 180 most popular npm packages. It is found that on average each package has 2.3 Islands of Knowledge, which is possibly explained by the finding that npm packages tend to have only one main contributor. In a survey, the maintainers of 50 packages are contacted and asked for opinions on the results produced by the Tool. Together with their responses, this thesis reports on experiences made with the pilot Tool and how future iterations could produce even more accurate statements about programming expertise distribution in developer teams.

Arduino basierte Sensorknoten für Fließgewässermonitoring (2017)

Diez, Sergei

This Work analyzes if a hardware prototype on an Arduino basis for an Adhoc Network can be created. The objective of the prototype development is, the creation of a sensor node with a modular design, where components can be easily changed. Furthermore the application area has requirements, which the node must fulfill. These requirements are derived from the Tmote Sky sensor node, therefore the new created sensor node must be a possible alternative for it and fulfill the same functions. For that purpose this study reviews some available Arduino microprocessors on their suitability for a sensor node. Later in the work the composition of the sensor node is documented. For this, the hardware and their costs are illustrated. The created hardware prototype allows, through easily changed radio modules, the covering of 433 MHz, 866 MHz and 2,40 GHz radio frequencies. At the end of the work, the sensor node prototype is used in an experiment to check for the suitability for water monitoring. For this, an experiment was performed on land and on water and the results evaluated. In the end the prototype fulfilled most of the requirements, but the cost was a little too high.

Towards an E-Participation Architecture Framework (EPArt-Framework) (2016)

Scherer, Sabrina

The provision of electronic participation services (e-participation) is a complex socio-technical undertaking that needs comprehensive design and implementation strategies. E-participation service providers, in the most cases administrations and governments, struggle with changing requirements that demand more transparency, better connectivity and increased collaboration among different actors. At the same time, less staff are available. As a result, recent research assesses only a minority of e-participation services as successful. The challenge is that the e-participation domain lacks comprehensive approaches to design and implement (e-)participation services. Enterprise Architecture (EA) frameworks have evolved in information systems research as an approach to guide the development of complex socio-technical systems. This approach can guide the design and implementation services, if the collection of organisations with the commonly held goal to provide participation services is understood as an E Participation Enterprise (EE). However, research & practice in the e participation domain has not yet exploited EA frameworks. Consequently, the problem scope that motivates this dissertation is the existing gap in research to deploy EA frameworks in e participation design and implementation. The research question that drives this research is: What methodical and technical guides do architecture frameworks provide that can be used to design and implement better and successful e participation? This dissertation presents a literature study showing that existing approaches have not covered yet the challenges of comprehensive e participation design and implementation. Accordingly, the research moves on to investigate established EA frameworks such as the Zachman Framework, TOGAF, the DoDAF, the FEA, the ARIS, and the ArchiMate for their use. While the application of these frameworks in e participation design and implementation is possible, an integrated approach is lacking so far. The synthesis of literature review and practical insights in design and implementation of e participation services from four projects show the challenges of adapting architecture frameworks for this domain. However, the research shows also the potential of a combination of the different approaches. Consequently, the research moves on to develop the E-Participation Architecture Framework (EPART-Framework). Therefore, the dissertation applies design science research including literature review and action research. Two independent settings test an initial EPART-Framework version. The results yield into the EPART-Framework presented in this dissertation. The EPART-Framework comprises of the EPART-Metamodel with six EPART-Viewpoints, which frame the stakeholder concerns: the Participation Scope, the Participant Viewpoint, the Participation Viewpoint, the Data & Information Viewpoint, the E-participation Viewpoint, and Implementation & Governance Viewpoint. The EPART-Method supports the stakeholders to design the EE and implement e participation and stores its output in an architecture description and a solution repository. It consists of five consecutive phases accompanied by requirements management: Initiation, Design, Implementation and Preparation, Participation, and Evaluation. The EPART-Framework fills the gap between the e participation domain and the enterprise architecture framework domain. The evaluation gives reasonable evidence that the framework is a valuable addition in academia and in practice to improve e-participation design and implementation. The same time, it shows opportunities for future research to extend and advance the framework.

Secure semantic web data management (2016)

Kasten, Andreas

Confidentiality, integrity, and availability are often listed as the three major requirements for achieving data security and are collectively referred to as the C-I-A triad. Confidentiality of data restricts the data access to authorized parties only, integrity means that the data can only be modified by authorized parties, and availability states that the data must always be accessible when requested. Although these requirements are relevant for any computer system, they are especially important in open and distributed networks. Such networks are able to store large amounts of data without having a single entity in control of ensuring the data's security. The Semantic Web applies to these characteristics as well as it aims at creating a global and decentralized network of machine-readable data. Ensuring the confidentiality, integrity, and availability of this data is therefore also important and must be achieved by corresponding security mechanisms. However, the current reference architecture of the Semantic Web does not define any particular security mechanism yet which implements these requirements. Instead, it only contains a rather abstract representation of security. This thesis fills this gap by introducing three different security mechanisms for each of the identified security requirements confidentiality, integrity, and availability of Semantic Web data. The mechanisms are not restricted to the very basics of implementing each of the requirements and provide additional features as well. Confidentiality is usually achieved with data encryption. This thesis not only provides an approach for encrypting Semantic Web data, it also allows to search in the resulting ciphertext data without decrypting it first. Integrity of data is typically implemented with digital signatures. Instead of defining a single signature algorithm, this thesis defines a formal framework for signing arbitrary Semantic Web graphs which can be configured with various algorithms to achieve different features. Availability is generally supported by redundant data storage. This thesis expands the classical definition of availability to compliant availability which means that data must only be available as long as the access request complies with a set of predefined policies. This requirement is implemented with a modular and extensible policy language for regulating information flow control. This thesis presents each of these three security mechanisms in detail, evaluates them against a set of requirements, and compares them with the state of the art and related work.

Attention dynamics of scientists on the web (2016)

Sennikova, Tatiana

This thesis analyzes the online attention towards scientists and their research topics. The studies compare the attention dynamics towards the winners of important scientific prizes with scientists who did not receive a prize. Web signals such as Wikipedia page views, Wikipedia edits, and Google Trends were used as a proxy for online attention. One study focused on the time between the creation of the article about a scientist and their research topics. It was discovered that articles about research topics were created closer to the articles of prize winners than to scientists who did not receive a prize. One possible explanation could be that the research topics are more closely related to the scientist who got an award. This supports that scientists who received the prize introduced the topics to the public. Another study considered the public attention trends towards the related research topics before and after a page of a scientist was created. It was observed that after a page about a scientist was created, research topics of prize winners received more attention than the topics of scientists who did not receive a prize. Furthermore, it was demonstrated that Nobel Prize winners get a lower amount of attention before receiving the prize than the potential nominees from the list of Citation Laureates of Thompson Reuters. Also, their popularity is going down faster after receiving it. It was also shown that it is difficult to predict the prize winners based on the attention dynamics towards them.

Simulation von alternativen Szenarien des Straßenverkehrs in Muskat (2016)

Tanveer, Asif

The aim of this work was to present the accident and traffic modeling of Oman (Muskat City) under theoretical assumptions by means of agent-based simulation. TRASS should be taken as the basis for the simulation environment. In addition, possible counter-measures should be proposed with regard to the high accident rate, which result from different simulation variants. It was not part of this work whether the theoretical assumptions by the simulation should actually be applied and implemented in reality. It was also necessary to check whether three different simulation variants could be represented differently by TRASS. The three variants were divided into simulation sequence with traffic light control, without traffic light control and finally with traffic light control, which however should be ignored with a probability of 70%. All three variants could produce different results. It has been shown that all three variants have advantages and disadvantages with respect to traffic flow and accident rate. Not to be neglected is the fact that this work is modeled, analyzed and evaluated exclusively with TRASS framework. All potentials and deficits thus flow into the overall framework of this work. Therefore, after critical observation, this statement was viewed from a single angle only: the theoretical assumptions of Oman and the modeling limits of TRASS. In order to be able to make a promising statement about the actual implementation of the proposals, further comprehensive analyzes and simulations are necessary in a much wider range of variants of transport for Oman.

Real-Time interaction in dialogmarketing (2016)

Poneta, Olaf

The aim of this thesis was to develop and to evaluate a method, which enables the utilization of traditional dialog marketing tools through the web. For this purpose, a prototype of a website with "extended real-time interaction (eEI)" capabilities has been implemented and tested. The prototype was evaluated by a methodology based on the five-dimensional "e-service quality" measure after Gwo-Guang Lee und Hsiu-Fen Lin. The Foundation of the "e-service quality" measure is the SERVQUAL-Model. A statistical analysis of the user study results showed a significant correlation between eEI and user satisfaction. Before the actual realization of eEI, the "Technology Acceptance Model" after Fred D. Davis was used to investigate currently used real-time interaction systems.

Silence is golden: reactive local topology control and geographic routing in wireless ad hoc and sensor networks (2016)

Neumann, Florentin

Reactive local algorithms are distributed algorithms which suit the needs of battery-powered, large-scale wireless ad hoc and sensor networks particularly well. By avoiding both unnecessary wireless transmissions and proactive maintenance of neighborhood tables (i.e., beaconing), such algorithms minimize communication load and overhead, and scale well with increasing network size. This way, resources such as bandwidth and energy are saved, and the probability of message collisions is reduced, which leads to an increase in the packet reception ratio and a decrease of latencies. Currently, the two main application areas of this algorithm type are geographic routing and topology control, in particular the construction of a node's adjacency in a connected, planar representation of the network graph. Geographic routing enables wireless multi-hop communication in the absence of any network infrastructure, based on geographic node positions. The construction of planar topologies is a requirement for efficient, local solutions for a variety of algorithmic problems. This thesis contributes to reactive algorithm research in two ways, on an abstract level, as well as by the introduction of novel algorithms: For the very first time, reactive algorithms are considered as a whole and as an individual research area. A comprehensive survey of the literature is given which lists and classifies known algorithms, techniques, and application domains. Moreover, the mathematical concept of O- and Omega-reactive local topology control is introduced. This concept unambiguously distinguishes reactive from conventional, beacon-based, topology control algorithms, serves as a taxonomy for existing and prospective algorithms of this kind, and facilitates in-depth investigations of the principal power of the reactive approach, beyond analysis of concrete algorithms. Novel reactive local topology control and geographic routing algorithms are introduced under both the unit disk and quasi unit disk graph model. These algorithms compute a node's local view on connected, planar, constant stretch Euclidean and topological spanners of the underlying network graph and route messages reactively on these spanners while guaranteeing the messages' delivery. All previously known algorithms are either not reactive, or do not provide constant Euclidean and topological stretch properties. A particularly important partial result of this work is that the partial Delaunay triangulation (PDT) is a constant stretch Euclidean spanner for the unit disk graph. To conclude, this thesis provides a basis for structured and substantial research in this field and shows the reactive approach to be a powerful tool for algorithm design in wireless ad hoc and sensor networking.

Techniques for optimized reasoning in description logic knowledge bases (2016)

Schon, Claudia

One of the main goals of the artificial intelligence community is to create machines able to reason with dynamically changing knowledge. To achieve this goal, a multitude of different problems have to be solved, of which many have been addressed in the various sub-disciplines of artificial intelligence, like automated reasoning and machine learning. The thesis at hand focuses on the automated reasoning aspects of these problems and address two of the problems which have to be overcome to reach the afore-mentioned goal, namely 1. the fact that reasoning in logical knowledge bases is intractable and 2. the fact that applying changes to formalized knowledge can easily introduce inconsistencies, which leads to unwanted results in most scenarios. To ease the intractability of logical reasoning, I suggest to adapt a technique called knowledge compilation, known from propositional logic, to description logic knowledge bases. The basic idea of this technique is to compile the given knowledge base into a normal form which allows to answer queries efficiently. This compilation step is very expensive but has to be performed only once and as soon as the result of this step is used to answer many queries, the expensive compilation step gets worthwhile. In the thesis at hand, I develop a normal form, called linkless normal form, suitable for knowledge compilation for description logic knowledge bases. From a computational point of view, the linkless normal form has very nice properties which are introduced in this thesis. For the second problem, I focus on changes occurring on the instance level of description logic knowledge bases. I introduce three change operators interesting for these knowledge bases, namely deletion and insertion of assertions as well as repair of inconsistent instance bases. These change operators are defined such that in all three cases, the resulting knowledge base is ensured to be consistent and changes performed to the knowledge base are minimal. This allows us to preserve as much of the original knowledge base as possible. Furthermore, I show how these changes can be applied by using a transformation of the knowledge base. For both issues I suggest to adapt techniques successfully used in other logics to get promising methods for description logic knowledge bases.

License usage analysis and license recommendation in open source software development (2016)

Schmidt, Kevin

The publication of open source software aims to support the reuse, the distribution and the general utilization of software. This can only be enabled by the correct usage of open source software licenses. Therefore associations provide a multitude of open source software licenses with different features, of which a developer can choose, to regulate the interaction with his software. Those licenses are the core theme of this thesis. After an extensive literature research, two general research questions are elaborated in detail. First, a license usage analysis of licenses in the open source sector is applied, to identify current trends and statistics. This includes questions concerning the distribution of licenses, the consistency in their usage, their association over a period of time and their publication. Afterwards the recommendation of licenses for specific projects is investigated. Therefore, a recommendation logic is presented, which includes several influences on a suitable license choice, to generate an at most applicable recommendation. Besides the exact features of a license of which a user can choose, different methods of ranking the recommendation results are proposed. This is based on the examination of the current situation of open source licensing and license suggestion. Finally, the logic is evaluated on the exemplary use-case of the 101companies project.

Lokalisation mittels Ultraschall (2016)

Opdenberg, Marcus

Die folgende Arbeit zeigt eine Möglichkeit auf, Lokalisierung eines Objektes mittels Ultraschall zu realisieren. Dazu werden drei bis fünf im Raum verteilte Sensoren genutzt, um anhand von Distanzinformationen die Position eines Objekts relativ zu den Positionen der Sensoren zu bestimmen. Eine Besonderheit besteht dabei darin, dass die Sensoren nahezu beliebig in der Ebene verteilt sein können. Ihre Anordnung wird vom System in der Kalibrierungsphase mit Unterstützung des Anwenders ermittelt. Dabei dürften ein gleichseitiges Dreieck, ein Quadrat oder Pentagramm je nach Sensoranzahl die besten Ergebnisse liefern. Um die relative Bewegung in eine Absolute zu übertragen, findet eine Umrechnung in Meter anhand der Taktung der Mikrocontroller, des Prescalers des verwendeten Timers und der Schallgeschwindigkeit statt.

Realisierung eines Schrittmotortreibers mit einem Atmel Mikrocontroller (2016)

Ziganow, Marcel

The present thesis deals with the realization of a stepper motor driver on an 8-bit microcontroller by the company Atmel. The focus is on the devel- opment of a current control, which allows microstepping in addition to the basic modes of operation like full- and halfstep. For this purpose, a PI con- troller is derived using physical and control engineering principles, which is implemented on the microcontroller. In this context, essential knowledge for the practical implementation will be discussed. In addition, the development of the hardware is documented, which is of great significance for the current measurement.

Developer profiling - extract developer expertise in a Django app (2015)

Rüther, Frederik

The identification of experts for a specific technology or framework produces a large benefit for collaborative software projects. Hence it reduces the communication overhead that is required to identify an expert on the fly. Therefore this thesis describes a tool and approach that can be used to identify an expert that has a specific skill-set. It will mainly focus on the skills and expertise of developers that use the Django framework. By adding more rules to our framework that approach could easily be extended for different technologies or frameworks. The paper will close with a case study on an open source project.

Haptische Rückfahrassistenz für Fahrzeuge mit 2-achsigem Anhänger (2015)

Brack, Marco

Die Arbeitsgruppe Echtzeitsysteme an der Universität Koblenz beschäftigt sich seit mehreren Jahren mit der Thematik autonomes und assistiertes Fahren. Eine große Herausforderung stellen in diesem Zusammenhang mehrgliedrige Fahrzeuge dar, deren Steuerung für den Fahrer während der Rückwärtsfahrt sehr anspruchsvoll ist. Um präzise Manöver zu ermöglichen, können elektronische Fahrerassistenzsysteme zum Einsatz kommen. Im Rahmen vorhergehender Arbeiten sind bereits einige Prototypen entstanden, von denen jedoch keiner eine geeignete Lösung für moderne, zweiachsige Anhänger darstellt. Im Rahmen dieser Arbeit wurde ein prototypisches Fahrerassistenzsystem entwickelt, wobei es noch weiterer Forschungs- und Entwicklungsarbeit bedarf, um das System straßentauglich zu machen.

An adaptive Software and System Architecture for Driver Assistance Systems applied to truck and trailer combinations (2015)

Wagner, Marco Andreas

Traditional Driver Assistance Systems (DAS) like for example Lane Departure Warning Systems or the well-known Electronic Stability Program have in common that their system and software architecture is static. This means that neither the number and topology of Electronic Control Units (ECUs) nor the presence and functionality of software modules changes after the vehicles leave the factory. However, some future DAS do face changes at runtime. This is true for example for truck and trailer DAS as their hardware components and software entities are spread over both parts of the combination. These new requirements cannot be faced by state-of-the-art approaches of automotive software systems. Instead, a different technique of designing such Distributed Driver Assistance Systems (DDAS) needs to be developed. The main contribution of this thesis is the development of a novel software and system architecture for dynamically changing DAS using the example of driving assistance for truck and trailer. This architecture has to be able to autonomously detect and handle changes within the topology. In order to do so, the system decides which degree of assistance and which types of HMI can be offered every time a trailer is connected or disconnected. Therefore an analysis of the available software and hardware components as well as a determination of possible assistance functionality and a re-configuration of the system take place. Such adaptation can be granted by the principles of Service-oriented Architecture (SOA). In this architectural style all functionality is encapsulated in self-contained units, so-called Services. These Services offer the functionality through well-defined interfaces whose behavior is described in contracts. Using these Services, large-scale applications can be built and adapted at runtime. This thesis describes the research conducted in achieving the goals described by introducing Service-oriented Architectures into the automotive domain. SOA deals with the high degree of distribution, the demand for re-usability and the heterogeneity of the needed components. It also applies automatic re-configuration in the event of a system change. Instead of adapting one of the frameworks available to this scenario, the main principles of Service-orientation are picked up and tailored. This leads to the development of the Service-oriented Driver Assistance (SODA) framework, which implements the benefits of Service-orientation while ensuring compatibility and compliance to automotive requirements, best-practices and standards. Within this thesis several state-of-the-art Service-oriented frameworks are analyzed and compared. Furthermore, the SODA framework as well as all its different aspects regarding the automotive software domain are described in detail. These aspects include a well-defined reference model that introduces and relates terms and concepts and defines an architectural blueprint. Furthermore, some of the modules of this blueprint such as the re-configuration module and the Communication Model are presented in full detail. In order to prove the compliance of the framework regarding state-of-the-art automotive software systems, a development process respecting today's best practices in automotive design procedures as well as the integration of SODA into the AUTOSAR standard are discussed. Finally, the SODA framework is used to build a full-scale demonstrator in order to evaluate its performance and efficiency.

Evolution-aware API analysis of developer skills (2015)

Aksu, Hakan

One task of executives and project managers in IT companies or departments is to hire suitable developers and to assign them to suitable problems. In this paper, we propose a new technique that directly leverages previous work experience of developers in a systematic manner. Existing evidence for developer expertise based on the version history of existing projects is analyzed. More specifically, we analyze the commits to a repository in terms of affected API usage. On these grounds, we associate APIs with developers and thus we assess API experience of developers. In transitive closure, we also assess programming domain experience.

Reactive construction of planar overlay graphs on unit disk graphs (2015)

Surberg, Freya

Geographic cluster based routing in ad-hoc wireless sensor networks is a current field of research. Various algorithms to route in wireless ad-hoc networks based on position information already exist. Among them algorithms that use the traditional beaconing approach as well as algorithms that work beaconless (no information about the environment is required besides the own position and the destination). Geographic cluster based routing with guaranteed message delivery can be carried out on overlay graphs as well. Until now the required planar overlay graphs are not being constructed reactively. This thesis proposes a reactive algorithm, the Beaconless Cluster Based Planarization (BCBP) algorithm, which constructs a planar overlay graph and noticeably reduces the number of messages required for that. Based on an algorithm for cluster based planarization it beaconlessly constructs a planar overlay graph in an unit disk graph (UDG). An UDG is a model for a wireless network in which every participant has the same sending radius. Evaluation of the algorithm shows it to be more efficient than the non beaconless variant. Another result of this thesis is the Beaconless LLRAP (BLLRAP) algorithm, for which planarity but not continued connectivity could be proven.

An Annotation-centric Approach to Similarity Management (2015)

Schmorleiz, Thomas

Software systems are often developed as a set of variants to meet diverse requirements. Two common approaches to this are "clone-and-owning" and software product lines. Both approaches have advantages and disadvantages. In previous work we and collaborators proposed an idea which combines both approaches to manage variants, similarities, and cloning by using a virtual platform and cloning-related operators. In this thesis, we present an approach for aggregating essential metadata to enable a propagate operator, which implements a form of change propagation. For this we have developed a system to annotate code similarities which were extracted throughout the history of a software repository. The annotations express similarity maintenance tasks, which can then either be executed automatically by propagate or have to be performed manually by the user. In this work we outline the automated metadata extraction process and the system for annotating similarities; we explain how the implemented system can be integrated into the workflow of an existing version control system (Git); and, finally, we present a case study using the 101haskell corpus of variants.

Distributed Query Processing for Federated RDF Data Management (2015)

Görlitz, Olaf

The publication of freely available and machine-readable information has increased significantly in the last years. Especially the Linked Data initiative has been receiving a lot of attention. Linked Data is based on the Resource Description Framework (RDF) and anybody can simply publish their data in RDF and link it to other datasets. The structure is similar to the World Wide Web where individual HTML documents are connected with links. Linked Data entities are identified by URIs which are dereferenceable to retrieve information describing the entity. Additionally, so called SPARQL endpoints can be used to access the data with an algebraic query language (SPARQL) similar to SQL. By integrating multiple SPARQL endpoints it is possible to create a federation of distributed RDF data sources which acts like one big data store. In contrast to the federation of classical relational database systems there are some differences for federated RDF data. RDF stores are accessed either via SPARQL endpoints or by resolving URIs. There is no coordination between RDF data sources and machine-readable meta data about a source- data is commonly limited or not available at all. Moreover, there is no common directory which can be used to discover RDF data sources or ask for sources which offer specific data. The federation of distributed and linked RDF data sources has to deal with various challenges. In order to distribute queries automatically, suitable data sources have to be selected based on query details and information that is available about the data sources. Furthermore, the minimization of query execution time requires optimization techniques that take into account the execution cost for query operators and the network communication overhead for contacting individual data sources. In this thesis, solutions for these problems are discussed. Moreover, SPLENDID is presented, a new federation infrastructure for distributed RDF data sources which uses optimization techniques based on statistical information.

Markov random field terrain classification for autonomous robots in unstructured terrain (2015)

Häselich, Marcel

This thesis addresses the problem of terrain classification in unstructured outdoor environments. Terrain classification includes the detection of obstacles and passable areas as well as the analysis of ground surfaces. A 3D laser range finder is used as primary sensor for perceiving the surroundings of the robot. First of all, a grid structure is introduced for data reduction. The chosen data representation allows for multi-sensor integration, e.g., cameras for color and texture information or further laser range finders for improved data density. Subsequently, features are computed for each terrain cell within the grid. Classification is performedrnwith a Markov random field for context-sensitivity and to compensate for sensor noise and varying data density within the grid. A Gibbs sampler is used for optimization and is parallelized on the CPU and GPU in order to achieve real-time performance. Dynamic obstacles are detected and tracked using different state-of-the-art approaches. The resulting information - where other traffic participants move and are going to move to - is used to perform inference in regions where the terrain surface is partially or completely invisible for the sensors. Algorithms are tested and validated on different autonomous robot platforms and the evaluation is carried out with human-annotated ground truth maps of millions of measurements. The terrain classification approach of this thesis proved reliable in all real-time scenarios and domains and yielded new insights. Furthermore, if combined with a path planning algorithm, it enables full autonomy for all kinds of wheeled outdoor robots in natural outdoor environments.

Matching keyword based queries to schema level indices over Linked Open Data (2015)

Hauck, Tobias

Im Rahmen dieser Arbeit soll eine Methodik erarbeitet werden, die englische, keyword-basierte Anfragen in SPARQL übersetzt und bewertet. Aus allen generierten SPARQL-Queries sollen die relevantesten ermittelt und ein Favorit bestimmt werden. Das Ergebnis soll in einer Nutzerevaluation bewertet werden.

Corpus-based empirical research in software engineering (2014)

Pek, Ekaterina

In the recent years, Software Engineering research has shown the rise of interest in the empirical studies. Such studies are often based on empirical evidence derived from corpora - collections of software artifacts. While there are established forms of carrying out empirical research (experiments, case studies, surveys, etc.), the common task of preparing the underlying collection of software artifacts is typically addressed in ad hoc manner. In this thesis, by means of a literature survey we show how frequently software engineering research employs software corpora and using a developed classification scheme we discuss their characteristics. Addressing the lack of methodology, we suggest a method of corpus (re-)engineering and apply it to an existing collection of Java projects. We report two extensive empirical studies, where we perform a broad and diverse range of analyses on the language for privacy preferences (P3P) and on object-oriented application programming interfaces (APIs). In both cases, we are driven by the data at hand, by the corpus itself, discovering the actual usage of the languages.

Eine systematische Literaturstudie zu beaconless Algorithmen für drahtlose Ad-hoc- und Sensornetze (2014)

Vivas Estevao, Daniel

Wireless sensor networks (WSN) are computer networks consisting of sensor nodes.In position-based protocols nodes broadcast messages containing their position information periodically. These messages are called beacons. The use of beacons however has downsides, which led to the emerging of beaconless algorithms. Despite their importance in the research area of computer networks and to the best of our knowledge, beaconless algorithms have not been systematically surveyed. The aim of this work is a comprehensive, systematic review of beaconless algorithms since the turn of the millennium. Relevant articles are categorized based on their similarities and their differences are compared. Thus, this work serves as a reference to the current state of research of beaconless algorithms and as a basis for finding research gaps.

Entwicklung eines "Homecomputers" auf Basis eines AVR-Microcontrollers (2014)

Sallie, Christoph

Im Verlauf der vergangenen Jahre wurden unter der Leitung von Dr. Merten Joost basierend auf Microcontrollern der ATMega-Reihe verschiedene Projekte zur Ansteuerung der Peripheriegeräte eines Computers realisiert. Hierzu zählen unter anderem die Abfrage einer Tastatur, die Ausgabe von Audio- und Videosignalen sowie eine Programmierumgebung mit eigener Programmiersprache. Ziel dieser Arbeit ist es, die gesammelten Projekte zu verbinden, um als Ergebnis einen eigenständigen "Homecomputer" zu erhalten, der per Tastatur angesteuert werden können soll und über eine Audio- und Videoausgabe verfügen soll. Dabei wird eine SD-Karte als Speichermedium dienen, das per Tastatureingabe über eine Art Shell verwaltet werden kann.

Sensorknoten Netzwerk für In Situ-Temperaturerhebung von Wasseroberflächen in Fließgewässern (2014)

Yousefi, Amir ; Taflinski, Ansgar ; Neumann, Florentin ; Frey, Hannes

In diesem Bericht wird der Einsatz von drahtlosen Sensornetzen zur Temperaturmessung in Fließgewässern untersucht. Es wird dargestellt, inwieweit solche Netze als Bindeglied zwischen Fernerkundung und stationären Sensoren eingesetzt werden können. Es werden die Anforderungen an Sensornetze für die Anwendung Gewässermonitoring ermittelt und eine prototypische Realisierung von Netzknoten für ein solches Sensornetz dargestellt. Als Ergebnis dieser Arbeit werden die Genauigkeit von Temperaturmessungen mit solchen Sensorknoten im Vergleich zu einem Temperaturlogger als Referenzsystem dargestellt. Die Messungen zeigen, dass eine vergleichsweise gute Messgenauigkeit zu geringen Kosten erreichbar ist. Durch Weiterentwicklung des hier dargestellten Prototypen steht für die Temperaturüberwachung in Gewässern ein vielversprechendes und kostengünstiges neues Messinstrument zur Verfügung. Dieses kann auf der einen Seite in tieferen Regionen Gewässertemperaturen messen, als dies mit Fernerkundung möglich ist, und auf der anderen Seite eine höhere räumliche Auflösung als stationäre Messstationen erreichen. Zusätzlich dienen die Literaturrecherche und die Formulierung der Kriterien einer Eingrenzung des Anwendungsbereichs für weiterführende Arbeiten.

Apple ][ Emulation on an AVR Microcontroller (2014)

Strauch, Maximilian

Der Apple ][ war einer der drei ersten kompletten Computersysteme auf dem Markt. Von April 1977 an wurde er rund 16 Jahre lang mehrere Millionen mal verkauft. Entwickelt wurde dieser 8 Bit Homecomputer von Steve Wozniak und Steve Jobs. Sie ebneten damit den Weg für den Macintosh und das heute gut bekannte Unternehmen Apple. Diese Arbeit beschreibt die Implementierung eines Softwareemulators für das komplette Apple ][ Computersystem auf nur einem Atmel AVR Microcontroller. Die größte Herausforderung besteht darin, dass der Microcontroller nur eine geringfügig höhere Taktrate als die zu emulierende Hardware hat. Dies erfordert eine effiziente Emulation der CPU und Speicherverwaltung, die nachfolgend zusammen mit der Laufzeitumgebung für die Emulation vorgestellt wird. Weiterhin wird die Umsetzung des Emulators mit Display und Tastatur in Hardware naher erläutert. Mit dieser Arbeit wird die erfolgreiche Entwicklung eines portablen Apple ][ Emulators, von der Software über die Hardware bis hin zu einem Prototypen, vorgestellt.

Anonymisierbare Kommunikation innerhalb verteilter Anwendungen durch Kopplung des MAppLab-RPC-Framework mit dem mPart-API-Framework (2014)

Schmeiser, Arne Fritjof

The increased networking of devices has established the usage of distributed applications as a common method in software development. Despite the demand of anonymity in using distributed applications, software frameworks still lack appropriate support in developing them. Building anonymous communicating applications therefore often results in an expensive individual approach. This work integrates an approach for anonymous communication using remote procedure calls into a software framework for building distributed applications. This also includes the design, development, and prototypical implementation of a binding for the MAppLab Remote Procedure Call Framework on the basis of the mPartAPI Framework. Furthermore the resulting prototype will be tested in an exemplary scenario.

Entwicklung einer Gesichtserkennenden Software zur Erfassung und Analyse von Personenströmen (2014)

Schens, Artur

Diese Bachelorarbeit befasst sich mit der Entwicklung und Implementierung einer Gesichtserkennenden Software, die in der Lage ist Personenströme zurnerkennen und zu protokollieren. Dabei wird, ausgehend von den speziellen Anforderungen der Bildverarbeitung die entstandene Softwarearchitektur und deren Implementation vorgestellt. Zusätzlich wird zur Implementation ein Webinterface entwickelt welches die Verwaltung der Daten vereinfachen soll. Abschließend werden weitere Verfahren der Gesichtserkennung vorgestellt und gegen das eingesetzte Verfahren verglichen. Zum Schluss wird die implementierte Software evaluiert.

Untersuchung codebasierter Governance in Online-Communities (2014)

Thesing, Tobias

Community-Plattformen im Internet verwenden codebasierte Governance, um ihre hohe Anzahl an Nutzerbeiträgen zu verwalten. Dazu gehören alle Arten von Funktionalitäten, mit denen die Community Nutzerbeiträge in irgendeiner Form direkt oder indirekt beurteilen kann. Diese Arbeit erklärt zunächst die Bedeutung codebasierter Governance und der verschiedenen dafür nutzbaren Funktionalitäten. Anschließend werden die erfolgreichsten 50 Community-Plattformen auf codebasierte Governance untersucht. Das Ergebnis zeigt die Zusammenhänge zwischen dem Aufbau einer Plattform, der Beschaσffenheit der Nutzerbeiträge und der darauf ausübbaren codebasierten Governance auf.

Mining Social Media: Methods and Approaches for Content Analysis (2014)

Naveed, Nasir

Web 2.0 provides technologies for online collaboration of users as well as the creation, publication and sharing of user-generated contents in an interactive way. Twitter, CNET, CiteSeerX, etc. are examples of Web 2.0 platforms which facilitate users in these activities and are viewed as rich sources of information. In the platforms mentioned as examples, users can participate in discussions, comment others, provide feedback on various issues, publish articles and write blogs, thereby producing a high volume of unstructured data which at the same time leads to an information overload. To satisfy various types of human information needs arising from the purpose and nature of the platforms requires methods for appropriate aggregation and automatic analysis of this unstructured data. In this thesis, we propose methods which attempt to overcome the problem of information overload and help in satisfying user information needs in three scenarios. To this end, first we look at two of the main challenges of sparsity and content quality in Twitter and how these challenges can influence standard retrieval models. We analyze and identify Twitter content features that reflect high quality information. Based on this analysis we introduce the concept of "interestingness" as a static quality measure. We empirically show that our proposed measure helps in retrieving and filtering high quality information in Twitter. Our second contribution relates to the content diversification problem in a collaborative social environment, where the motive of the end user is to gain a comprehensive overview of the pros and cons of a discussion track which results from social collaboration of the people. For this purpose, we develop the FREuD approach which aims at solving the content diversification problem by combining latent semantic analysis with sentiment estimation approaches. Our evaluation results show that the FREuD approach provides a representative overview of sub-topics and aspects of discussions, characteristic user sentiments under different aspects, and reasons expressed by different opponents. Our third contribution presents a novel probabilistic Author-Topic-Time model, which aims at mining topical trends and user interests from social media. Our approach solves this problem by means of Bayesian modeling of relations between authors, latent topics and temporal information. We present results of application of the model to the scientific publication datasets from CiteSeerX showing improved semantically cohesive topic detection and capturing shifts in authors" interest in relation to topic evolution.

Reconstruction and Visualization of Neuronal Pathways with Applications in Neuroscience (2014)

Röttger, Diana

Diffusion imaging captures the movement of water molecules in tissue by applying varying gradient fields in a magnetic resonance imaging (MRI)-based setting. It poses a crucial contribution to in vivo examinations of neuronal connections: The local diffusion profile enables inference of the position and orientation of fiber pathways. Diffusion imaging is a significant technique for fundamental neuroscience, in which pathways connecting cortical activation zones are examined, and for neurosurgical planning, where fiber reconstructions are considered as intervention related risk structures. Diffusion tensor imaging (DTI) is currently applied in clinical environments in order to model the MRI signal due to its fast acquisition and reconstruction time. However, the inability of DTI to model complex intra-voxel diffusion distributions gave rise to an advanced reconstruction scheme which is known as high angular resolution diffusion imaging (HARDI). HARDI received increasing interest in neuroscience due to its potential to provide a more accurate view of pathway configurations in the human brain. In order to fully exploit the advantages of HARDI over DTI, advanced fiber reconstructions and visualizations are required. This work presents novel approaches contributing to current research in the field of diffusion image processing and visualization. Diffusion classification, tractography, and visualizations approaches were designed to enable a meaningful exploration of neuronal connections as well as their constitution. Furthermore, an interactive neurosurgical planning tool with consideration of neuronal pathways was developed. The research results in this work provide an enhanced and task-related insight into neuronal connections for neuroscientists as well as neurosurgeons and contribute to the implementation of HARDI in clinical environments.

Interactive visualizations for the linking and search process of heterogeneous information on the web (2013)

Hienert, Daniel

The amount of information on the Web is constantly increasing and also there is a wide variety of information available such as news, encyclopedia articles, statistics, survey data, stock information, events, bibliographies etc. The information is characterized by heterogeneity in aspects such as information type, modality, structure, granularity, quality and by its distributed nature. The two primary techniques by which users on the Web are looking for information are (1) using Web search engines and (2) browsing the links between information. The dominant mode of information presentation is mainly static in the form of text, images and graphics. Interactive visualizations offer a number of advantages for the presentation and exploration of heterogeneous information on the Web: (1) They provide different representations for different, very large and complex types of information and (2) large amounts of data can be explored interactively using their attributes and thus can support and expand the cognition process of the user. So far, interactive visualizations are still not an integral part in the search process of the Web. The technical standards and interaction paradigms to make interactive visualization usable by the mass are introduced only slowly through standardatization organizations. This work examines how interactive visualizations can be used for the linking and search process of heterogeneous information on the Web. Based on principles in the areas of information retrieval (IR), information visualization and information processing, a model is created, which extends the existing structural models of information visualization with two new processes: (1) linking of information in visualizations and (2) searching, browsing and filtering based on glyphs. The Vizgr toolkit implements the developed model in a web application. In four different application scenarios, aspects of the model will be instantiated and are evaluated in user tests or examined by examples.

Dokumentation zu Routing-Tabellen und Forwarding (2013)

Steffes-Enn, Dirk

In dieser Studienarbeit sollen verschiedene Routing-Lookup Algorithmen aufgelistet und verglichen werden, mit denen eine Routing-Tabelle erstellt und angepasst werden kann. Dazu werden hier nur dynamische Verfahren in Betracht gezogen. Allgemein wird die Funktionsweise einer Routing-Tabelle erklärt und drei Verfahren bzw. Algorithmen analysiert und bewertet. Die Algorithmen werden anhand von Beispielen erläutert und in einem abschließenden Kapitel gegenüber gestellt. Dabei werden die Vor- und Nachteile der einzelnen Verfahren aufgelistet.

Automated Reasoning Embedded in Question Answering (2013)

Pelzer, Björn

This dissertation investigates the usage of theorem provers in automated question answering (QA). QA systems attempt to compute correct answers for questions phrased in a natural language. Commonly they utilize a multitude of methods from computational linguistics and knowledge representation to process the questions and to obtain the answers from extensive knowledge bases. These methods are often syntax-based, and they cannot derive implicit knowledge. Automated theorem provers (ATP) on the other hand can compute logical derivations with millions of inference steps. By integrating a prover into a QA system this reasoning strength could be harnessed to deduce new knowledge from the facts in the knowledge base and thereby improve the QA capabilities. This involves challenges in that the contrary approaches of QA and automated reasoning must be combined: QA methods normally aim for speed and robustness to obtain useful results even from incomplete of faulty data, whereas ATP systems employ logical calculi to derive unambiguous and rigorous proofs. The latter approach is difficult to reconcile with the quantity and the quality of the knowledge bases in QA. The dissertation describes modifications to ATP systems in order to overcome these obstacles. The central example is the theorem prover E-KRHyper which was developed by the author at the Universität Koblenz-Landau. As part of the research work for this dissertation E-KRHyper was embedded into a framework of components for natural language processing, information retrieval and knowledge representation, together forming the QA system LogAnswer. Also presented are additional extensions to the prover implementation and the underlying calculi which go beyond enhancing the reasoning strength of QA systems by giving access to external knowledge sources like web services. These allow the prover to fill gaps in the knowledge during the derivation, or to use external ontologies in other ways, for example for abductive reasoning. While the modifications and extensions detailed in the dissertation are a direct result of adapting an ATP system to QA, some of them can be useful for automated reasoning in general. Evaluation results from experiments and competition participations demonstrate the effectiveness of the methods under discussion.

E-Hyper Tableaux with Distinct Object Identifiers (2013)

Bender, Markus

E-KRHyper is a versatile theorem prover and model generator for firstorder logic that natively supports equality. Inequality of constants, however, has to be given by explicitly adding facts. As the amount of these facts grows quadratically in the number of these distinct constants, the knowledge base is blown up. This makes it harder for a human reader to focus on the actual problem, and impairs the reasoning process. We extend E-Hyper- underlying E-KRhyper tableau calculus to avoid this blow-up by implementing a native handling for inequality of constants. This is done by introducing the unique name assumption for a subset of the constants (the so called distinct object identifiers). The obtained calculus is shown to be sound and complete and is implemented into the E-KRHyper system. Synthetic benchmarks, situated in the theory of arrays, are used to back up the benefits of the new calculus.

The Quaternality of Simulation: An Event/Non-Event Approach (2012)

Lautenbach, Kurt

Dualizing marked Petri nets results in tokens for transitions (t-tokens). A marked transition can strictly not be enabled, even if there are sufficient "enabling" tokens (p-tokens) on its input places. On the other hand, t-tokens can be moved by the firing of places. This permits flows of t-tokens which describe sequences of non-events. Their benefiit to simulation is the possibility to model (and observe) causes and effects of non-events, e.g. if something is broken down.

Applying Probability Propagation Nets (2012)

Lautenbach, Kurt ; Susewind, Kerstin

In this paper, we demonstrate by means of two examples how to work with probability propagation nets (PPNs). The fiirst, which comes from the book by Peng and Reggia [1], is a small example of medical diagnosis. The second one comes from [2]. It is an example of operational risk and is to show how the evidence flow in PPNs gives hints to reduce high losses. In terms of Bayesian networks, both examples contain cycles which are resolved by the conditioning technique [3].

Probability Propagation Nets and Duality (2012)

Lautenbach, Kurt ; Susewind, Kerstin

The paper deals with a specific introduction into probability propagation nets. Starting from dependency nets (which in a way can be considered the maximum information which follows from the directed graph structure of Bayesian networks), the probability propagation nets are constructed by joining a dependency net and (a slightly adapted version of) its dual net. Probability propagation nets are the Petri net version of Bayesian networks. In contrast to Bayesian networks, Petri nets are transparent and easy to operate. The high degree of transparency is due to the fact that every state in a process is visible as a marking of the Petri net. The convenient operability consists in the fact that there is no algorithm apart from the firing rule of Petri net transitions. Besides the structural importance of the Petri net duality there is a semantic matter; common sense in the form of probabilities and evidencebased likelihoods are dual to each other.

Cheops für VNUML - Erstellen und beobachten einer VNUML-Simulation per Mausklick (2012)

Bayer, Martin

Cheops für VNUML - Erstellen und beobachten einer VNUML-Simulation per MausklickrnEs wird untersucht, wie Virtual Network User Mode Linux (VNUML), eine Software zur Simulation von Rechnernetzen, die aus virtualisierten Linux Instanzen aufgebaut werden, für den Benutzer besser handhabbar gemacht werden kann. Mit dem Linux-Paket VNUML, welches die dateigesteuerte Konfiguration virtueller Betriebssysteminstanzen ermöglicht, erhält der Anwender die Möglichkeit, komplexe Netzwerktopologien zu simulieren. Verschiedene Netzwerküberwachungsprogramme werden auf ihre Fähigkeit hin untersucht, eine laufende VNUML-Simulation zu erfassen und sinnvoll abzubilden. Dabei soll der Benutzer einen schnellen Überblick über die Funktion der simulierten Netzwerkumgebung, sowie nach Möglichkeit auch über deren Topologie erhalten können. Das Programm Cheops, welches der Netzwerküberwachung dient, wird erweitert, um nicht nur eine laufende Simulation abbilden und beobachten zu können, sondern darüber hinaus in der Lage zu sein, in jedem Schritt der Arbeit mit VNUML eingesetzt zu werden. Das erweiterte Programm gestattet sowohl die Erstellung der VNUML-Topologiedatei, als auch das Starten und Steuern der Simulation. Damit werden der lange Kommandozeilenaufruf, sowie das Editieren der Konfigurationsdatei, durch einfach zu benutzende Funktionen in einer grafischen Oberfläche (GUI) ersetzt. Zur schnellen Kontrolle der vollen Funktionsfähigkeit der gestarteten Simulation sind keine weiteren Eingaben oder Konfigurationen nötig. Ebenso kann eine differenzierte Beobachtung verschiedener Netzwerkdienste während der Laufzeit der Simulation erfolgen. Die hierzu nötigen Werkzeuge sind im Paket Cheops für VNUML ebenfalls enthalten und speziell zur Anwendung mit VNUML-Simulationen vorkonfiguriert.

Systematisches Management inhaltsbezogener Informationen in der Entwicklung von Lernsoftware (2012)

Grützner, Ines

Education and training of the workforce have become an important competitive factor for companies because of the rapid technological changes in the economy and the corresponding ever shorter innovation cycles. Traditional training methods, however, are limited in terms of meeting the resulting demand for education and training in a company, which continues to grow and become faster all the time. Therefore, the use of technology-based training programs (that is, courseware) is increasing because courseware enables self-organized and self-paced learning and, through integration into daily work routines, allows optimal transfer of knowledge and skills, resulting in high learning outcome. To achieve these prospects, high-quality courseware is required, with quality being defined as supporting learners optimally in achieving their learning goals. Developing high-quality courseware, however, usually requires more effort and takes longer than developing other programs, which limits the availability of this courseware in time and with the required quality. This dissertation therefore deals with the research question of how courseware has to be developed in order to produce high-quality courseware with less development effort and shorter project duration. In addition to its high quality, this courseware should be optimally aligned to the characteristics and learning goals of the learners as well as to the planned usage scenarios for the knowledge and skills being trained. The IntView Method for the systematic and efficient development of high-quality courseware was defined to answer the research question of this dissertation. It aims at increasing the probability of producing courseware in time without exceeding project schedules and budgets while developing a high-quality product optimally focused on the target groups and usage scenarios. The IntView Methods integrates those execution variants of all activities and activity steps required to develop high-quality courseware, which were identified in a detailed analysis of existing courseware development approaches as well as production approaches from related fields, such as multimedia, web, or software engineering, into a systematic process that in their interaction constitute the most efficient way to develop courseware. The main part of the proposed method is therefore a systematic process for engineering courseware that encompasses all courseware lifecycle phases and integrates the activities and methods of all disciplines involved in courseware engineering, including a lifecycle encompassing quality assurance, into a consolidated process. This process is defined as a lifecycle model as well as a derived process model in the form of a dependency model in order to optimally support courseware project teams in coordinating and synchronizing their project work. In addition to the models, comprehensive, ready-to-apply enactment support materials are provided, consisting of work sheets and document templates that include detailed activity descriptions and examples. The evaluation of the IntView Method proved that the method together with the enactment support materials enables efficient as well as effective courseware development. The projects and case studies conducted in the context of this evaluation demonstrate that, on the one hand, the method is easily adaptable to the production of different kinds of courseware or to different project contexts, and, on the other hand, that it can be used efficiently and effectively.

Data Provenance and Destiny in Distributed Environments (2012)

Ringelstein, Christoph

Modern Internet and Intranet techniques, such as Web services and virtualization, facilitate the distributed processing of data providing improved flexibility. The gain in flexibility also incurs disadvantages. Integrated workflows forward and distribute data between departments and across organizations. The data may be affected by privacy laws, contracts, or intellectual property rights. Under such circumstances of flexible cooperations between organizations, accounting for the processing of data and restricting actions performed on the data may be legally and contractually required. In the Internet and Intranet, monitoring mechanisms provide means for observing and auditing the processing of data, while policy languages constitute a mechanism for specifying restrictions and obligations. In this thesis, we present our contributions to these fields by providing improvements for auditing and restricting the data processing in distributed environments. We define formal qualities of auditing methods used in distributed environments. Based on these qualities, we provide a novel monitoring solution supporting a data-centric view on the distributed data processing. We present a solution for provenance-aware policies and a formal specification of obligations offering a procedure to decide whether obligatory processing steps can be met in the future.

Bridging Technological Spaces: Towards the Combination of Model-Driven Engineering and Ontology Technologies (2011)

Walter, Tobias

Model-Driven Engineering (MDE) aims to raise the level of abstraction in software system specifications and increase automation in software development. Modelware technological spaces contain the languages and tools for MDE that software developers take into consideration to model systems and domains. Ontoware technological spaces contain ontology languages and technologies to design, query, and reason on knowledge. With the advent of the Semantic Web, ontologies are now being used within the field of software development, as well. In this thesis, bridging technologies are developed to combine two technological spaces in general. Transformation bridges translate models between spaces, mapping bridges relate different models between two spaces, and, integration bridges merge spaces to new all-embracing technological spaces. API bridges establish interoperability between the tools used in the space. In particular, this thesis focuses on the combination of modelware and ontoware technological spaces. Subsequent to a sound comparison of languages and tools in both spaces, the integration bridge is used to build a common technological space, which allows for the hybrid use of languages and the interoperable use of tools. The new space allows for language and domain engineering. Ontology-based software languages may be designed in the new space where syntax and formal semantics are defined with the support of ontology languages, and the correctness of language models is ensured by the use of ontology reasoning technologies. These languages represent a core means for exploiting expressive ontology reasoning in the software modeling domain, while remaining flexible enough to accommodate varying needs of software modelers. Application domains are conceptually described by languages that allow for defining domain instances and types within one domain model. Integrated ontology languages may provide formal semantics for domain-specific languages and ontology technologies allow for reasoning over types and instances in domain models. A scenario in which configurations for network device families are modeled illustrates the approaches discussed in this thesis. Furthermore, the implementation of all bridging technologies for the combination of technological spaces and all tools for ontology-based language engineering and use is illustrated.

DiaLex - The Emergence of Dialects (2011)

Klein, Christian

This dissertation investigates the emergence of dialects in a model of a multi-agent simulation based on neural networks that is developed within this thesis. First the linguistic foundation of language is illustrated. Besides discussing some important definitions of language, this is achieved by giving a summary of the evolutionary steps in language evolution followed by an overview of the elements of human modern languages including the ways of language change. Subsequently some examples of socially learned animals" communicative behaviour and its formations of dialects are shown. In the following the computational and mathematical basis are to be explained. Besides the expressions model and simulation, these comprehend the setup of multi-agent simulations and the functionality of artificial neural networks. Based on the abovementioned basics the model of this dissertation is derived and described in a detailed way. Results drawn out of several hundreds of simulation runs are explicated thereafter. Each destructive factor defined in the model is examined separately and its domain is divided into intervals with different effects on the outcome of the simulation. Furthermore, existing interdependences between the single factors and the process of language merging after a prior dialect divide are shown. Results and outlook are followed by specification, draft, architecture, a detailed illustration of the implementation and a user guide of the tool named DiaLex. DiaLex is a java based tool providing users the opportunity to simulate and analyse the influence of different destructive factors on dialect formation within a commonly used language of one or multiple communities of agents.

Towards Improving the Understanding of Image Semantics by Gaze-based Tag-to-Region Assignments (2011)

Walber, Tina ; Scherp, Ansgar ; Staab, Steffen

Eye-trackers have been used in the past to identify visual foci in images, find task-related image regions, or localize affective regions in images. However, they have not been used for identifying specific objects in images. In this paper, we investigate whether it is possible to assign image regions showing specific objects with tags describing these objects by analyzing the users' gaze paths. To this end, we have conducted an experiment with 20 subjects viewing 50 image-tag-pairs each. We have compared the tag-to-region assignments for nine existing and four new fixation measures. In addition, we have investigated the impact of extending region boundaries, weighting small image regions, and the number of subjects viewing the images. The paper shows that a tag-to-region assignment with an accuracy of 67% can be achieved by using gaze information. In addition, we show that multiple regions on the same image can be differentiated with an accuracy of 38%.

Installation des Quagga RMTI Daemons auf einem Linksys WRT54G (2011)

Pennig, Josef

An der Universität Koblenz wurde mit dem RMTI (RIP with Metric based Topology Investigation) eine Erweiterung zu RIP entwickelt, die das Counting-to-Infinity Problem beheben soll. Eine lauffähige Implementierung des RMTI Algorithmus, auf Basis des RIP Daemons der Quagga Software Routing Suite, liegt vor. Openwrt ist ein, auf Linux basierendes, quelloffenes Betriebssystem für Router, wie z.B. den WRT54G der Firma Linksys. Die Möglichkeiten der Konfiguration der Router mit Openwrt gehen weit über die der original Firmware hinaus. So können die Router mit Software aus dem Linux-Bereich erweitert werden. Ziel dieser Studienarbeit ist die Installation des RMTI Daemons in Openwrt auf den Linksys WRT54G Routern der AG Rechnernetze. Anschließend sollen typische Netzwerksituationen aufgebaut und das Verhalten der Router untersucht werden.

Nagios unter VNUML (2011)

Römer, Torsten

Die Arbeit beschreibt den Einsatz der Monitoringsoftware Nagios in einem mit VNUML erstellten virtuellen Rechnernetzwerk.

Creating an abstract physics layer for Simspark (2011)

Held, Andreas

This paper documents the development of an abstract physics layer (APL) for Simspark. After short introductions to physics engines and Simspark, reasons why an APL was developed are explained. The biggest part of this paper describes the new design and why certain design choices were made based on requirements that arose during developement. It concludes by explaining how the new design was eventually implemented and what future possibilities the new design holds.

Discovering and exploiting semantics in folksonomies (2011)

Abbasi, Rabeeh

Folksonomies are Web 2.0 platforms where users share resources with each other. Furthermore, they can assign keywords (called tags) to the resources for categorizing and organizing the resources. Numerous types of resources like websites (Delicious), images (Flickr), and videos (YouTube) are supported by different folksonomies. The folksonomies are easy to use and thus attract the attention of millions of users. Together with the ease they offer, there are also some problems. This thesis addresses different problems of folksonomies and proposes solutions for these problems. The first problem occurs when users search for relevant resources in folksonomies. Often, the users are not able to find all relevant resources because they don't know which tags are relevant. The second problem is assigning tags to resources. Although many folksonomies (like Delicious) recommend tags for the resources, other folksonomies (like Flickr) do not recommend any tags. Tag recommendation helps the users to easily tag their resources. The third problem is that tags and resources are lacking semantics. This leads for example to ambiguous tags. The tags are lacking semantics because they are freely chosen keywords. The automatic identification of the semantics of tags and resources helps in reducing problems that arise from this freedom of the users in choosing the tags. This thesis proposes methods which exploit semantics to address the problems of search, tag recommendation, and the identification of tag semantics. The semantics are discovered from a variety of sources. In this thesis, we exploit web search engines, online social communities and the co-occurrences of tags as sources of semantics. Using different sources for discovering semantics reduces the efforts to build systems which solve the problems mentioned earlier. This thesis evaluates the proposed methods on a large scale data set. The evaluation results suggest that it is possible to exploit the semantics for improving search, recommendation of tags, and automatic identification of the semantics of tags and resources.

Marrying model-driven engineering and ontology technologies: the TwoUse approach (2011)

Parreiras, Fernando Silva

The semantic web and model-driven engineering are changing the enterprise computing paradigm. By introducing technologies like ontologies, metadata and logic, the semantic web improves drastically how companies manage knowledge. In counterpart, model-driven engineering relies on the principle of using models to provide abstraction, enabling developers to concentrate on the system functionality rather than on technical platforms. The next enterprise computing era will rely on the synergy between both technologies. On the one side, ontology technologies organize system knowledge in conceptual domains according to its meaning. It addresses enterprise computing needs by identifying, abstracting and rationalizing commonalities, and checking for inconsistencies across system specifications. On the other side, model-driven engineering is closing the gap among business requirements, designs and executables by using domain-specific languages with custom-built syntax and semantics. In this scenario, the research question that arises is: What are the scientific and technical results around ontology technologies that can be used in model-driven engineering and vice versa? The objective is to analyze approaches available in the literature that involve both ontologies and model-driven engineering. Therefore, we conduct a literature review that resulted in a feature model for classifying state-of-the-art approaches. The results show that the usage of ontologies and model-driven engineering together have multiple purposes: validation, visual notation, expressiveness and interoperability. While approaches involving both paradigms exist, an integrated approach for UML class-based modeling and ontology modeling is lacking so far. Therefore, we investigate the techniques and languages for designing integrated models. The objective is to provide an approach to support the design of integrated solutions. Thus, we develop a conceptual framework involving the structure and the notations of a solution to represent and query software artifacts using a combination of ontologies and class-based modeling. As proof of concept, we have implemented our approach as a set of open source plug-ins -- the TwoUse Toolkit. The hypothesis is that a combination of both paradigms yields improvements in both fields, ontology engineering and model-driven engineering. For MDE, we investigate the impact of using features of the Web Ontology Language in software modeling. The results are patterns and guidelines for designing ontology-based information systems and for supporting software engineers in modeling software. The results include alternative ways of describing classes and objects and querying software models and metamodels. Applications show improvements on changeability and extensibility. In the ontology engineering domain, we investigate the application of techniques used in model-driven engineering to fill the abstraction gap between ontology specification languages and programming languages. The objective is to provide a model-driven platform for supporting activities in the ontology engineering life cycle. Therefore, we study the development of core ontologies in our department, namely the core ontology for multimedia (COMM) and the multimedia metadata ontology. The results are domain-specific languages that allow ontology engineers to abstract from implementation issues and concentrate on the ontology engineering task. It results in increasing productivity by filling the gap between domain models and source code.

Location Provider (2011)

Hebel, Tobias

In dieser Arbeit wurde gemäß den in Kapitel 1.3 definierten Anforderungen ein System entwickelt, um mobile und in der Rechenleistung beschränkte Geräte wie Mobiltelefone und PDAs sowohl im Freien als auch in geschlossenen Räumen verorten zu können. Der eingeschränkten Leistungsfähigkeit der Geräte wird durch die Umsetzung einer Client-Server Lösung Rechnung getragen, bei der der Client als Sensorträger dient, der Daten aus seiner Umgebung registriert und über ein Kommunikationsnetz zur weiteren Berechnung an einen Server überträgt. Die Datenübertragung ist als Webservice realisiert, der auf offenen Standards wie XML und SOAP basiert und leicht um weitere Funktionen erweitert werden kann.

Improvements to the RMTI network routing daemon implementation and preparation of a public release (2011)

Monreal, Michael

Routing with Metric based Topology Investigation (RMTI) is an algorithm meant to extend distance-vector routing protocols. It is under research and development at the University of Koblenz-Landau since 1999 and currently implemented on top of the well-known Routing Information Protocol (RIP). Around midyear 2009, the latest implementation of RMTI included a lot of deprecated functionality. Because of this, the first goal of this thesis was the reduction of the codebase to a minimum. Beside a lot of reorganization and a general cleanup, this mainly involved the removal of some no longer needed modes as well as the separation of the formerly mandatory XTPeer test environment. During the second part, many test series were carried out in order to ensure the correctness of the latest RMTI implementation. A replacement for XTPeer was needed and several new ways of testing were explored. In conjunction with this thesis, the RMTI source code was finally released to the public under a free software license.

Integrating OpenWrt routers in VNUML-virtualized networks (2011)

Taflinski, Ansgar

Die Arbeit beschäftigt sich mit der für Router und Kleingeräte entwickelten Linux-Distribution OpenWrt. Im ersten Teil der Arbeit wird die Erstellung von Softwarepaketen für OpenWrt erläutert und eine Anzeige- und Konfigurationskomponente für die Dateien des Quagga RIP-Daemons für die Benutzeroberfläche LuCI erstellt. Im zweiten Teil wird der Aufbau eines Testnetzwerkes mit OpenWrt Routern dokumentiert, sowie die Anbindung an VNUML-virtualisierte Netzwerke.

Linkless normal form for ALC concepts (2010)

Schon, Claudia

Knowledge compilation is a common technique for propositional logic knowledge bases. A given knowledge base is transformed into a normal form, for which queries can be answered efficiently. This precompilation step is expensive, but it only has to be performed once. We apply this technique to concepts defined in the Description Logic ALC. We introduce a normal form called linkless normal form for ALC concepts and discuss an efficient satisability test for concepts given in this normal form. Furthermore, we will show how to efficiently calculate uniform interpolants of precompiled concepts w.r.t. a given signature.

A Petri net approach for propagating probabilities and mass functions (2010)

Lautenbach, Kurt

This paper has a twofold concern. First, to show that probability propagation nets (PPNs) can be derived from formulae for conditional probabilities. Second, to show that PPNs are usable for (local) propagations of mass distributions, too, if the inscriptions are suitably adapted.

fnnlib: a flexible C++ library for recurrent neural network simulations (2010)

Faßbender, Dennis

This thesis introduces fnnlib, a C++ library for recurrent neural network simulations that I developed between October 2009 and March 2010 at Osaka University's Graduate School of Engineering. After covering the theory behind recurrent neural networks, backpropagation through time, recurrent neural networks with parametric bias, continuous-time recurrent neural networks, and echo state networks, the design of the library is explained. All of the classes as well as their interrelationships are presented along with reasons as to why certain design decisions were made. Towards the end of the thesis, a small practical example is shown. Also, fnnlib is compared to other neural network libraries.

Heuristic methods to determine an optimal preconfiguration of E-KRHyper (2010)

Eifler, Timo

Diese Arbeit behandelt verschiedene Ansätze zur Ermittlung einer Heuristik, welche zur Bestimmung einer optimalen Konfiguration des Theorembeweisers E-KRHyper eingesetzt werden soll. Es wird erläutert, wie der Beweiser durch eine angepasste Voreinstellung optimiert werden kann und die erarbeiteten Ansätze zur Ermittlung dieser Voreinstellung werden vorgestellt. Anhand der erzielten Ergebnisse werden die Ansätze anschließend bewertet und für eines der vorgestellten Verfahren wird außerdem eine Idee zur Implementierung vorgestellt.

A large-scale analysis of Java API usage (2010)

Starek, Jürgen

This thesis presents an analysis of API usage in a large corpus of Java software retrieved from the open source repositories hosted at SourceForge. Most larger software projects use software libraries, which offer a public "application programming interface" or API as an interface for the programmer. In order to facilitate the transition between different APIs, there are emerging research projects in the field of automated API migration. However, there is a lack of basic statistical background information about in-the-wild usage of APIs as such measurements have, until now, only been done on rather small corpora. We thus present an analysis method suitable for measurements with large corpora. First, we create a corpus of open source projects hosted on SourceForge, as well as a corpus of software libraries. Then, all projects in the corpus are compiled with an instrumented compiler. We use a compiler plugin for javac that gives detailed information about every method created by the compiler. This information is stored in a database and analyzed.

Hybrid multi-agent systems: modeling, specification and verification (2010)

Mohammed, Ammar

Specifying behaviors of multi-agent systems (MASs) is a demanding task, especially when applied in safety-critical systems. In the latter systems, the specification of behaviors has to be carried out carefully in order to avoid side effects that might cause unwanted or even disastrous behaviors. Thus, formal methods based on mathematical models of the system under design are helpful. They not only allow us to formally specify the system at different levels of abstraction, but also to verify the consistency of the specified systems before implementing them. The formal specification aims a precise and unambiguous description of the behavior of MASs, whereas the verification aims at proving the satisfaction of specified requirements. A behavior of an agent can be described as discrete changes of its states with respect to external or internal actions. Whenever an action occurs, the agent moves from one state to another one. Therefore, an efficient way to model this type of discrete behaviors is to use a kind of state transition diagrams such as finite automata. One remarkable advantage of such transition diagrams is that they lend themselves formal analysis techniques using model checking. The latter is an automatic verification technique which determines whether given properties are satisfied within a model underlying a particular system. In realistic physical environments, however, it is necessary to consider continuous behaviors in addition to discrete behaviors of MASs. Examples of those type of behaviors include the movement of a soccer agent to kick off or to go to the ball, the process of putting out the fire by a fire brigade agent in a rescue scenario, or any other behaviors that depend on any timed physical law. The traditional state transition diagrams are not sufficient to combine these types of behaviors. Hybrid automata offer an elegant method to capture such types of behaviors. Hybrid automata extend regular state transition diagrams with methods that deal with those continuous actions such that the state transition diagrams are used to model the discrete changes of behaviors, while differential equations are used to model the continuous changes. The semantics of hybrid automata make them accessible to formal verification by means of model checking. The main goal of this thesis is to approach hybrid automata for specifying and verifying behaviors of MASs. However, specifying and and verifying behaviors of MASs by means of hybrid automata raises several issues that should be considered. These issues include the complexity, modularity, and the expressiveness of MASs' models. This thesis addresses these issues and provides possible solutions to tackle them.

Simulation großer Netzwerke in der VNUML-Umgebung (2010)

Garbe, Andreas

So far VNUML (Virtual Network User Mode Linux) has been used by the group for Computer Networks at the University of Koblenz in such a way as to test its own protocol enhancement for RIP (Routing Information Protocol) on strengths and weaknesses. The modified version of RIP is called RMTI (RIP with minimal topology information). In particular, special test scenarios have been used to investigate wether a Count-to-Infinity (CTI) problem can be completely avoided and how quickly the network converges after the failure or breakdown of a router. Tius thesis investigates whether the MTI enhancement also provides for better performance in larger networks. Furthermore, it will be investigated if it is worth using the script tool EDIV ((spanish: Escenarios DIstribuidos con VNUML, english: Distributed Scenarios using VNUML) due to its enhanced scalability and whether the distribution of an XML scenario on several computers has a significant impact on the convergence time. Apart from simulations, test scenarios will be developed and tested in order to generate results about the efficiency and scalability of the Distance Vector Routing Protocol.

Anschluß eines GPS-Moduls an einen Mikrocontroller und Versuch der Präzitionssteigerung (2010)

Schneider, Mario

In einer Welt, die immer mehr durch den Einsatz von Technik geprägt wird, gewinnen Systeme, welche eigenständig Aufgaben in einem vorgegebenen Kontext übernehmen können, mehr und mehr an Bedeutung. Solche Systeme werden als autonome Systeme bezeichnet, die ein eigenständiges Verhalten und Interaktionen mit ihrer Umwelt und anderen Systemen beinhalten. Zu diesen Systemen zählen auch autonome mobile Roboter. Sie sind sozusagen intelligente Fahrzeuge, die ihnen übertragene Aufgaben ohne menschliche Unterstützung durchführen können. Um ihre Umwelt wahrzunehmen, mit ihr interagieren und in ihr navigieren zu können benötigen diese Systeme verschiedene Arten von Sensoren. Somit ist die Robotikforschung stark interdisziplinär. Diese Arbeit befasst sich ausschliesslich mit dem Bereich der Navigation, insbesondere mit der Positionsbestimmung, welche für eine gute Navigation die Grundlage bildet. Ein heutzutage häufig benutztes, weltweit verfügbares System zur Positionsbestimmung ist GPS. Ziel dieser Arbeit ist der Anschluss eines GPS-Moduls an einen Mikrocontroller und der Versuch die Positionsgenauigkeit lokal zu präzisieren, um so einem autonomen System die Möglichkeit zur eröffnen, Aufgaben, die eine höhere Genauigkeit erfordern, zu bewerkstelligen.

Generating efficient test oracles from specifications (2010)

Bender, Markus

This minor thesis shows a way to optimise a generated oracle to achieve shorter runtimes. Shorter runtimes of test cases allows the execution of more test cases in the same time. The execution of more test cases leads to a higher confidence in the software-quality. Oracles can be derived from specifications. However specifications are used for different purposes and therefore are not necessarily executable. Even if the are executable it might be with only a high runtime. Those two facts come mostly from the use of quantifiers in the logic. If the quantifier-range is not bounded, respectively if the bounds are outside the target language-datatype-limits, the specification is too expressive to be exported into a program. Even if the bounds inside the used datatype-limits, the quantification is represented as a loop which leads to a runtime blowup, especially if quantifiers are nested. This work explains four different possibilities to reduce the execution time of the oracle by manipulating the quantified formular whereas this approach is only applicable if the quantified variables are of type Integer.

Verifying Dijkstra's Algorithm with KeY (2010)

Klasen, Volker

Die Entwicklung von Algorithmen im Sinne des Algorithm Engineering geschieht zyklisch. Der entworfene Algorithmus wird theoretisch analysiert und anschließend implementiert. Nach der praktischen Evaluierung wird der Entwurf anhand der gewonnenen Kenntnisse weiter entwickelt. Formale Verifffizierung der Implementation neben der praktischen Evaluierung kann den Entwicklungsprozess verbessern. Mit der Java Modeling Language (JML) und dem KeY tool stehen eine einfache Spezififfkationssprache und ein benutzerfreundliches, automatisiertes Verififfkationstool zur Verfügung. Diese Arbeit untersucht, inwieweit das KeY tool für die Verifffizierung von komplexeren Algorithmen geeignet ist und welche Rückmeldungen für Algorithmiker aus der Verififfkation gewonnen werden können.Die Untersuchung geschieht anhand von Dijkstras Algorithmus zur Berechnung von kürzesten Wegen in einem Graphen. Es sollen eine konkrete Implementation des Standard-Algorithmus und anschließend Implementationen weiterer Varianten verifffiziert werden. Dies ahmt den Entwicklungsprozess des Algorithmus nach, um in jeder Iteration nach möglichen Rückmeldungen zu suchen. Bei der Verifffizierung der konkreten Implementation merken wir, dass es nötig ist, zuerst eine abstraktere Implementation mit einfacheren Datenstrukturen zu verififfzieren. Mit den dort gewonnenen Kenntnissen können wir dann die Verifikation der konkreten Implementation fortführen. Auch die Varianten des Algorithmus können dank der vorangehenden Verififfkationen verifiziert werden. Die Komplexität von Dijkstras Algorithmus bereitet dem KeY tool einige Schwierigkeiten bezüglich der Performanz, weswegen wir während der Verifizierung die Automatisierung etwas reduzieren müssen. Auf der anderenrn Seite zeigt sich, dass sich aus der Verifffikation einige Rückmeldungen ableiten lassen.

PAPEL: Syntax and Semantics for Provenance-Aware Policy Definition (2010)

Ringelstein, Christoph ; Staab, Steffen

The processing of data is often restricted by contractual and legal requirements for protecting privacy and IPRs. Policies provide means to control how and by whom data is processed. Conditions of policies may depend on the previous processing of the data. However, existing policy languages do not provide means to express such conditions. In this work we present a formal model and language allowing for specifying conditions based on the history of data processing. We base the model and language on XACML.

Implementierung des Spanning-Tree-Algorithmus IEEE 802.1D (2010)

Janke, Andreas Sebastian

In this thesis a Java program is developed that can be used to visualize networks previously described in configuration files. These networks must consist of layer 2 switches and hosts only. After loading such a configuration file, the program will visualize the network, and the spanning tree algorithm IEEE 802.1D may be started. The program allows the user to modify specific attributes of switches and hosts. The hosts will be able to exchange messages. The switches are realized as threads so that they can run independently and parallel to each other. The absence of central coordination and control prevents the switches from sharing global knowledge. This characteristic renders the implementation closer to the way an actual network functions.

Statistische Konvergenzanalyse des RIP-Routingprotokolls (2010)

Jakobs, Marcel

A network like the internet is a set of subnets that are connected to each other by a router. A router is a computer, containing multiple network devices to be connected to multiple subnets. So, it is able to forward packages from one subnet to another. A network can be represented as a graph with its routers as vertices and subnets as edges. This graph is called the topology of the network. A packet send to a host outside the own subnet usually will be send first to the so-called default router. This router (like any router) contains a table (the so-called forwarding table) with every subnet. Additionally for each net, the table contains the router through which the subnet can be reached best. So, the packet will be forwarded from router to router until it reaches the destination subnet. On this way every router looks up in its forwarding table for the best next router. A routing protocol takes care of the automatic exchange of informations between the routers to build the forwarding tables and keep them up to date. If the forwarding tables of all routers are up to date the network is called convergent. The time needed to build or update the routing tables is called the convergence time The RIP routing protocol is a well known and well explored distance vector protocol. But there are only few examinations about the convergence properties (e.g. the time needed to converge or the traffic volume produced by the routing messages). This work tries to examine a relationship between the topology properties of a network and the convergence properties of the rip routing protocol. Therefore, over 5000 single measurements were performed and statistically analyzed. Mathematical formulas have been derived from the results that are able to approximate the convergence properties of a network from its topology properties.

VNUML mit dem Protokoll-Analyser Wireshark (2010)

Zebaze Dongho, Mireille Kathy

In this work, some network protocols with Wireshark Protokollanalyser should be observed and described the deal with them. Wireshark is an offshoot of "Ethereal", one of the most popular protocol analyzer. Wireshark analysis network traffic, draws on it and make it clear . For the simulation of the network is used VNUML. Since VNUML can only be used under Linux, andLinux is running as a virtual machine in between to work in Windows to be able to.

Automatisierte Auswertung von Testfällen mit XTPeer (2010)

Mo, Kim-Sun

RMTI (RIP with Metric based Topology Investigation) wurde in der AG Rechnernetze an der Universität Koblenz-Landau entwickelt. RMTI stellt eine Erweiterung zum RIP (Routing Information Protocol) dar, die das Konvergenzverhalten bei Netzwerkveränderungen, insb. bei Routingschleifen, verbessern soll. Dies geschieht durch Erkennen von Routingschleifen und Reduzieren des Count-to-infinity Problems. Um dieses gewünschte Verhalten nachweisen zu können, bedarf eine reichhaltige Evaluierung des RMTI- Algorithmus. Hierzu wurde in der gleichen Arbeitsgruppe die Client-/Server-Applikation XTPeer entwickelt. In Kombination mit anderen Software wie VNUML und Quagga Routing Suite lässt sich per XT-Peer der Algorithmus evaluieren. Die Applikation XTPeer generiert durch die Simulationen Daten. Diese können in Form von XML konforme SDF-Dateien exportiert werden. Diese können ohne weitere Auswertungen wieder in die XTPeer Applikation importiert werden. Die Evaluierung der Simulationen findet automatisiert nur an der aktuellen Simulation statt. Evaluierung über mehrere Simulationen muss der Benutzer manuell berechnen. Um diese Evaluierungsarbeiten für den Benutzer zu vereinfachen, verfolgt die vorliegende Diplomarbeit daher das Ziel, die XTPeer Applikation mit einem Auswertungsmodul zu erweitern. Die Auswertungen soll sich über alle gespeicherten Simulationsdaten und nicht wie bisher nur über die aktuell laufende Simulation erstrecken. Dies ermöglicht bessere statistisch verwertbare Aussagen. Zusätzlich können diese Auswertungsergebnisse grafisch unterstrichen werden.

Konzept einer public key infrastruktur in iCity (2010)

Magnus, Sebastian ; Maron, Markus

Dieses Dokument schlägt ein Konzept für eine Personal Key Infrastruktur in iCity vor. Über ein Trust Center (TC) ausgestellte Zertiffkate gewährleisten einen sicheren Schlüsselaustausch mit nachweisbarer Authentisierung des Kommunikationspartners, Abhörsicherheit sowie Unverf älschtheit und Nachweisbarkeit der Nachrichten. Das gemeinsam vertrauensw ürdige TC muss während der Kommunikation nicht erreichbar sein. Es erhält lediglich öffentliche Informationen. Das Konzept stellt mehrere Sicherheitsstufen vor, die sichere Identiffkation und Anonymität unterschiedlich gewichten.

A public key infrastructure in ambient information and transaction systems (2010)

Magnus, Sebastian ; Maron, Markus

Conventional security infrastructures in the Internet cannot be directly adopted to ambient systems, especially if based on short-range communication channels: Personal, mobile devices are used and the participants are present during communication, so privacy protection is a crucial issue. As ambient systems cannot rely on an uninterrupted connection to a Trust Center, certiffed data has to be veriffed locally. Security techniques have to be adjusted to the special environment. This paper introduces a public key infrastructure (PKI) to provide secure communication channels with respect to privacy, confidentiality, data integrity, non-repudiability, and user or device authentication. It supports three certiffcate levels with a different balance between authenticity and anonymity. This PKI is currently under implementation as part of the iCity project.

Multi-agent systems: modeling and verification using hybrid automata (2010)

Mohammed, Ammar ; Furbach, Ulrich

Hybrid automata are used as standard means for the specification and analysis of dynamical systems. Several researches have approached them to formally specify reactive Multi-agent systems situated in a physical environment, where the agents react continuously to their environment. The specified systems, in turn, are formally checked with the help of existing hybrid automata verification tools. However, when dealing with multi-agent systems, two problems may be raised. The first problem is a state space problem raised due to the composition process, where the agents have to be parallel composed into an agent capturing all possible behaviors of the multi-agent system prior to the verification phase. The second problem concerns the expressiveness of verification tools when modeling and verifying certain behaviors. Therefore, this paper tackles these problems by showing how multi-agent systems, specified as hybrid automata, can be modeled and verified using constraint logic programming(CLP). In particular, a CLP framework is presented to show how the composition of multi-agent behaviors can be captured dynamically during the verification phase. This can relieve the state space complexity that may occur as a result of the composition process. Additionally, the expressiveness of the CLP model flexibly allows not only to model multi-agent systems, but also to check various properties by means of the reachability analysis. Experiments are promising to show the feasibility of our approach.

Extending the reach and power of deductive program verification (2009)

Klebanov, Vladimir

Software is vital for modern society. The efficient development of correct and reliable software is of ever-growing importance. An important technique to achieve this goal is deductive program verification: the construction of logical proofs that programs are correct. In this thesis, we address three important challenges for deductive verification on its way to a wider deployment in the industry: 1. verification of thread-based concurrent programs 2. correctness management of verification systems 3. change management in the verification process. These are consistently brought up by practitioners when applying otherwise mature verification systems. The three challenges correspond to the three parts of this thesis (not counting the introductory first part, providing technical background on the KeY verification approach). In the first part, we define a novel program logic for specifying correctness properties of object-oriented programs with unbounded thread-based concurrency. We also present a calculus for the above logic, which allows verifying actual Java programs. The calculus is based on symbolic execution resulting in its good understandability for the user. We describe the implementation of the calculus in the KeY verification system and present a case study. In the second part, we provide a first systematic survey and appraisal of factors involved in reliability of formal reasoning. We elucidate the potential and limitations of self-application of formal methods in this area and give recommendations based on our experience in design and operation of verification systems. In the third part, we show how the technique of similarity-based proof reuse can be applied to the problems of industrial verification life cycle. We address issues (e.g., coping with changes in the proof system) that are important in verification practice, but have been neglected by research so far.

VNUML-Installation im Windows-Pool an der Universität Koblenz-Landau (2009)

Wendling, Mario

Die Motivation für diese Arbeit bestand darin, den Studierenden in den Rechnerpools der Universität Koblenz die Möglichkeit zu geben, mit der Simulationssoftware VNUML (Virtual Network User Mode Linux) zu arbeiten. Eingesetzt wird diese Software in den Vorlesungen und Übungen zu Rechnernetzen I und II, was eine Anwendung der Software für die Studenten unumgänglich macht. In der Vergangenheit gab es jedoch immer wieder Probleme bei der Installation und Einrichtung auf den privaten Rechnern, obwohl in früheren Studienarbeiten mehrfach vereinfachte Installationsroutinen entwickelt worden waren. Ein weiteres Problem für die Verwendung von VNUML stellt auch die Tatsache dar, dass die Software nur in einer Linux-Umgebung lauffähig ist. Da aber nicht alle Studierenden das Betriebssystem Linux benutzen und viele vor einer Installation allein zur Verwendung von VNUML zurückschrecken, war es schon länger angedacht, diese Software an den Rechnern der Universität zur Verfügung zu stellen. In dieser Arbeit wird der Prozess beschrieben, wie eine Installation der VNUML-Software in den Rechnerpools möglich war, welche Probleme dabei aufgetreten sind und welche Alternativen zur gewählten Vorgehensweise möglich gewesen wären. Das Ergebnis bietet auch eine sehr einfache Installation für den privaten Anwender, ohne dass hierfür eine eigenständige Linux-Installation nötig wäre. Auch wurden während der Entwicklung immer weitere Verbesserungen vorgenommen, welche die Anwenderfreundlichkeit der endgültigen Lösung weiter erhöhten. Die Möglichkeiten und Ideen sind dabei auch so vielfältig, dass sich die Arbeitsgruppe noch weiter mit diesem Thema beschäftigen wird und weitere Optimierungen vorgenommen werden können.

Evaluation von Cicero : Akzeptanztest der Diskussionsplattform im Rahmen einer Fallstudie (2009)

Neumann, Jens

Cicero ist eine asynchrone Diskussionsplattform, die im Rahmen der Arbeitsgruppe Informationssysteme und Semantic Web (ISWeb) der Universität Koblenz-Landau entwickelt wurde. Die webbasierte Anwendung folgt dem Gedanken eines semantischen Wikis und soll insbesondere beim Arbeitsablauf von Entwurfsprozessen eingesetzt werden. Dabei verwendet Cicero ein restriktives Argumentationsmodell, das einerseits strukturierte Diskussionen von schwierigen Prozessen fördert und andererseits den Entscheidungsfindungsprozess unterstützt. Im Zentrum der Arbeit steht die Evaluation von Cicero, wobei im vorhergehenden theoretischen Teil die Hintergründe und Funktionsweisen vorgestellt werden und im nachfolgenden praktischen Teil die Anwendung anhand einer Fallstudie evaluiert wird. Die Studie wurde im Rahmen der Übungsveranstaltung zu Grundlagen der Datenbanken der Universität Koblenz im Wintersemester 2008/2009 durchgeführt , und die Studenten hatten die Aufgabe, einen Entwurfsprozess mit Hilfe von Cicero zu diskutieren. Über die erhobenen Daten der Fallstudie wird ein Akzeptanztest durchgeführt. Hierbei wird überprüft, ob die Benutzer Cicero positiv annehmen und die Methodik richtig anwenden. Denn aufgrund des vorgegebenen Argumentationsmodells müssen die Benutzer ihr Kommunikationsverhalten ändern und ihren herkömmlichen Diskussionsstil der Anwendung anpassen. Ziel der Evaluation ist es, kritische Erfolgsfaktoren im Umgang mit Cicero ausfindig zu machen. Anhand der identifizierten Schwachstellen werden abschließend gezielte Maßnahmen vorgeschlagen, die die Akzeptanz der Benutzer gegenüber Cicero erhöhen könnten.

An empirical study to evaluate the location of advertisement panels by using a mobile marketing tool (2009)

Magnus, Sebastian ; Maron, Markus

The efficiency of marketing campaigns is a precondition for business success. This paper discusses a technique to transfer advertisement content vie Bluetooth technology and collects market research information at the same time. Conventional advertisement media were enhanced by devices to automatically measure the number, distance, frequency and exposure time of passersby, making information available to evaluate both the wireless media as well as the location in general. This paper presents a study analyzing these data. A cryptographic one-way function protects privacy during data acquisition.

Evaluation & Convergence Analysis of RIP with metric based Topology Investigation (2009)

Kober, Manuel

Der RIPMTI-Algorithmus wurde entwickelt um die Schleifenerkennung in Rechnernetzen zu verbessern. Das Count-To-Infinity-Problem (kurz: CTI) führt dazu, dass ein Netzwerk nur sehr langsam in einen konvergenten Zustand gelangt. Der Hopcount-Wert 16, der als künstliche Beschränkung des CTI eingeführt wurde, beschränkt leider auch die maximale Topologietiefe eines Netzwerkes. Diese Arbeit soll zeigen wie sich eine schrittweise Erhöhung des Hopcount-Wertes und darüber hinaus die Änderung der Updatezeiten jedes Routers auf die Konvergenzzeiten unterschiedlicher Netzwerk-Szenarios auswirkt.

Administration von physikalischen & virtuellen Switches, Cisco 3500 XL vs. VDE (2009)

Algin, Suat ; Ayalp, Serdar

Ein Switch (engl. Schalter; auch Weiche) ist eine Netzwerk-Komponente zur Verbindung mehrerer Computer bzw. Netz-Segmente in einem lokalen Netzwerk (LAN). Da Switches den Netzwerkverkehr analysieren und logische Entscheidungen treffen, werden sie auch als intelligente Hubs bezeichnet. Die Funktionsweise eines Switches ist der einer Bridge sehr ähnlich, daher wurde anfangs auch der Begriff Multi-Port-Bridge genutzt 1. Ziel der Diplomarbeit ist es, eine Dokumentation auf die Beine zu stellen, der interessierten Studenten der Informationstechnologie die Möglichkeit bietet, einerseits anhand von physikalischen Switches Administrationsaufgaben nachzuempfinden und andererseits anhand von virtuellen Switches größere Netzwerktopologien aufzubauen. Diese Virtualisierung wird durch das von Virtual Square entwickelte Tool VDE erreicht. Die physikalischen Switches bestehen aus vier Catalyst 3500 XL. Im Laufe dieser Arbeit wird sowohl die Bedienung der einzelnen Systeme untereinander, wie auch die Vernetzung der virtuellen Switches mit den physikalischen Switches erläutert. In diesem Zusammenhang wird auch auf Protokolle und Methoden wie das Spanning Tree Protokoll oder die Virtualisierung eines Netzes durch VLANs eingegangen. Zum Schluss kann der Leser das gelernte in einigen praktischen Aufgaben anwenden.

Using Constraint Logic Programming for Modeling and Verifying Hierarchical Hybrid Automata (2009)

Mohammed, Ammar ; Stolzenburg, Frieder

Hybrid systems are the result of merging the two most commonly used models for dynamical systems, namely continuous dynamical systems defined by differential equations and discrete-event systems defined by automata. One can view hybrid systems as constrained systems, where the constraints describe the possible process flows, invariants within states, and transitions on the one hand, and to characterize certain parts of the state space (e.g. the set of initial states, or the set of unsafe states) on the other hand. Therefore, it is advantageous to use constraint logic programming (CLP) as an approach to model hybrid systems. In this paper, we provide CLP implementations, that model hybrid systems comprising several concurrent hybrid automata, whose size is only straight proportional to the size of the given system description. Furthermore, we allow different levels of abstraction by making use of hierarchies as in UML statecharts. In consequence, the CLP model can be used for analyzing and testing the absence or existence of (un)wanted behaviors in hybrid systems. Thus in summary, we get a procedure for the formal verification of hybrid systems by model checking, employing logic programming with constraints.

Virtualisierung von Mehrprozessorsystemen mit Echtzeitanwendungen (2009)

Kaiser, Robert

This work is about three subjects: Virtualisation, real-time computing and parallel computing. Taken by itself, each of these subjects has already been wellresearched, however, when considering all three together, as is necessary when looking at embedded systems, numerous questions as well as new possibilities arise. In this work we develop models describing the behaviour and requirements of real-time applications which execute in a hierarchy of processes as they do when running in a virtual machine. Also, the real-time capabilities of existing virtual machines are evaluated and new interfaces for virtualisation of multiprocessor machines which take into account the characteristics of embedded systems"specifically real-time computing" are defined, implemented and tested. This enables safe, secure and efficient coexistence of programs with largely differing time constraints within separate virtual machines on a single, common multiprocessor computer.

Transaktionskonzept für die TGraphenbibliothek JGraLab (2009)

Monte Barreto, José Angel

Im Rahmen dieser Diplomarbeit wird ein Transaktionskonzept für die aktuelle Implementationsversion der TGraphenbibliothek JGraLab Carnotaurus umgesetzt. Nach einer grundlegenden Einführung in das Konzept der TGraphen werden die relevanten Implementationsdetails der TGraphenbibliothek erläutert. Anschließend erfolgt ein konzeptueller Entwurf, in dem die formalen Grundlagen des Transaktionskonzepts beschrieben werden. Das aus der Datenbankwelt bekannte ACID-Paradigma für Transaktionen dient dabei als wissenschaftliche Grundlage. In einem nächsten Schritt erfolgt der objektorientierte Feinentwurf der Integration des zu entwickelnden Transaktionskonzepts in das vorhandene Gesamtsystem, anhand dessen die Implementation durchgeführt wird. Eine Analyse und Bewertung des umgesetzten Transaktionskonzepts (vor allem im Hinblick auf den Speicherverbrauch und das Laufzeitverhalten) schließen die Arbeit ab.

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