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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.
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.
Avoidance of routing loops
(2009)
We introduce a new routing algorithm which can detect routing loops by evaluating routing updates more thoroughly. Our new algorithm is called Routing with Metric based Topology Investigation (RMTI), which is based on the simple Routing Information Protocol (RIP) and is compatible to all RIP versions. In case of a link failure, a network can reorganize itself if there are redundant links available. Redundant links are only available in a network system like the internet if the topology contains loops. Therefore, it is necessary to recognize and to prevent routing loops. A routing loop can be seen as a circular trace of a routing update information which returns to the same router, either directly from the neighbor router or via a loop topology. Routing loops could consume a large amount of network bandwidth and could impact the endtoend performance of the network. Our RMTI approach is capable to improve the efficiency of Distance Vector Routing.
In dieser Arbeit wurden insgesamt fünf verwandte, aber variante Definitionen der Hermite-Normalform vorgestellt, angefangen bei der ursprünglichen Version von Charles Hermite. Anschließend wurden vier Basisalgorithmen zur Berechnung der Hermite-Normalform ganzzahliger Matrizen im Detail und anhand von vollständigen Beispielen präsentiert. Hierbei wurde vor allem Wert darauf gelegt, linear-algebraische Grundlagen wie beispielsweise die Verwendung von Permutationsmatrizen für unimodulare Spaltenoperationen verständlich zu vermitteln.
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.
In this paper we describe a network for distributing personalized information within a pervasive university. We discuss the system architecture of our Bluetooth-based CampusNews-system, both, from the administrator and the user viewpoint. We furthermore present first statistical data about the usage of the partial installation at the Koblenz campus together with an outlook to future work.
In this paper we describe a network for distributing personalized Information in a metropolitan area. We discuss the system architecture of our Bluetooth-based information system as well as the reasoning process that fits users" needs with potential messages. We furthermore present our findings on parallelizing Bluetooth connection setup and performance.
CAMPUS NEWS - artificial intelligence methods combined for an intelligent information network
(2008)
In this paper we describe a network for distributing personalised information with the usage of artificial intelligence methods. Reception of this information should be possible with everyday mobile equipment. Intelligent filtering and spam protection aim at integrating this technology into our environment. Information on the system architecture and usage of the installation are also presented.
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.
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.
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.
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.
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.
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.
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.
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.
Semantic desktop environments aim at improving the effectiveness and efficiency of users carrying out daily tasks within their personal information management infrastructure (PIM). They support the user by transferring and exploiting the explicit semantics of data items across different PIM applications. Whether such an approach does indeed reach its aim of facilitating users" life and—if so—to which extent, however, remains an open question that we address in this paper with the first summative evaluation of a semantic desktop approach. We approach the research question exploiting our own semantic desktop infrastructure, X-COSIM. As data corpus, we have used over 100 emails and 50 documents extracted from the organizers of a conference-like event at our university. The evaluation has been carried out with 18 subjects. We have developed a test environment to evaluate COSIMail and COSIFile, two semantic PIM applications based on X-COSIM. As result, we have found a significant improvement for typical PIM tasks compared to a standard desktop environment.
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.
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.