@phdthesis{Loeffler2021, author = {L{\"o}ffler, Andre}, title = {Constrained Graph Layouts: Vertices on the Outer Face and on the Integer Grid}, edition = {1. Auflage}, publisher = {W{\"u}rzburg University Press}, address = {W{\"u}rzburg}, isbn = {978-3-95826-146-4}, doi = {10.25972/WUP-978-3-95826-147-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-215746}, school = {W{\"u}rzburg University Press}, pages = {viii, 161}, year = {2021}, abstract = {Constraining graph layouts - that is, restricting the placement of vertices and the routing of edges to obey certain constraints - is common practice in graph drawing. In this book, we discuss algorithmic results on two different restriction types: placing vertices on the outer face and on the integer grid. For the first type, we look into the outer k-planar and outer k-quasi-planar graphs, as well as giving a linear-time algorithm to recognize full and closed outer k-planar graphs Monadic Second-order Logic. For the second type, we consider the problem of transferring a given planar drawing onto the integer grid while perserving the original drawings topology; we also generalize a variant of Cauchy's rigidity theorem for orthogonal polyhedra of genus 0 to those of arbitrary genus.}, subject = {Graphenzeichnen}, language = {en} } @phdthesis{Fink2014, author = {Fink, Martin}, title = {Crossings, Curves, and Constraints in Graph Drawing}, publisher = {W{\"u}rzburg University Press}, isbn = {978-3-95826-002-3 (print)}, doi = {10.25972/WUP-978-3-95826-003-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-98235}, school = {W{\"u}rzburg University Press}, pages = {222}, year = {2014}, abstract = {In many cases, problems, data, or information can be modeled as graphs. Graphs can be used as a tool for modeling in any case where connections between distinguishable objects occur. Any graph consists of a set of objects, called vertices, and a set of connections, called edges, such that any edge connects a pair of vertices. For example, a social network can be modeled by a graph by transforming the users of the network into vertices and friendship relations between users into edges. Also physical networks like computer networks or transportation networks, for example, the metro network of a city, can be seen as graphs. For making graphs and, thereby, the data that is modeled, well-understandable for users, we need a visualization. Graph drawing deals with algorithms for visualizing graphs. In this thesis, especially the use of crossings and curves is investigated for graph drawing problems under additional constraints. The constraints that occur in the problems investigated in this thesis especially restrict the positions of (a part of) the vertices; this is done either as a hard constraint or as an optimization criterion.}, subject = {Graphenzeichnen}, language = {en} } @phdthesis{Nogatz2023, author = {Nogatz, Falco}, title = {Defining and Implementing Domain-Specific Languages with Prolog}, doi = {10.25972/OPUS-30187}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301872}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {The landscape of today's programming languages is manifold. With the diversity of applications, the difficulty of adequately addressing and specifying the used programs increases. This often leads to newly designed and implemented domain-specific languages. They enable domain experts to express knowledge in their preferred format, resulting in more readable and concise programs. Due to its flexible and declarative syntax without reserved keywords, the logic programming language Prolog is particularly suitable for defining and embedding domain-specific languages. This thesis addresses the questions and challenges that arise when integrating domain-specific languages into Prolog. We compare the two approaches to define them either externally or internally, and provide assisting tools for each. The grammar of a formal language is usually defined in the extended Backus-Naur form. In this work, we handle this formalism as a domain-specific language in Prolog, and define term expansions that allow to translate it into equivalent definite clause grammars. We present the package library(dcg4pt) for SWI-Prolog, which enriches them by an additional argument to automatically process the term's corresponding parse tree. To simplify the work with definite clause grammars, we visualise their application by a web-based tracer. The external integration of domain-specific languages requires the programmer to keep the grammar, parser, and interpreter in sync. In many cases, domain-specific languages can instead be directly embedded into Prolog by providing appropriate operator definitions. In addition, we propose syntactic extensions for Prolog to expand its expressiveness, for instance to state logic formulas with their connectives verbatim. This allows to use all tools that were originally written for Prolog, for instance code linters and editors with syntax highlighting. We present the package library(plammar), a standard-compliant parser for Prolog source code, written in Prolog. It is able to automatically infer from example sentences the required operator definitions with their classes and precedences as well as the required Prolog language extensions. As a result, we can automatically answer the question: Is it possible to model these example sentences as valid Prolog clauses, and how? We discuss and apply the two approaches to internal and external integrations for several domain-specific languages, namely the extended Backus-Naur form, GraphQL, XPath, and a controlled natural language to represent expert rules in if-then form. The created toolchain with library(dcg4pt) and library(plammar) yields new application opportunities for static Prolog source code analysis, which we also present.}, subject = {PROLOG }, language = {en} } @phdthesis{Klein2014, author = {Klein, Dominik Werner}, title = {Design and Evaluation of Components for Future Internet Architectures}, issn = {1432-8801}, doi = {10.25972/OPUS-9313}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-93134}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2014}, abstract = {Die derzeitige Internetarchitektur wurde nicht in einem geplanten Prozess konzipiert und entwickelt, sondern hat vielmehr eine evolutionsartige Entwicklung hinter sich. Ausl{\"o}ser f{\"u}r die jeweiligen Evolutionsschritte waren dabei meist aufstrebende Anwendungen, welche neue Anforderungen an die zugrundeliegende Netzarchitektur gestellt haben. Um diese Anforderungen zu erf{\"u}llen, wurden h{\"a}ufig neuartige Dienste oder Protokolle spezifiziert und in die bestehende Architektur integriert. Dieser Prozess ist jedoch meist mit hohem Aufwand verbunden und daher sehr tr{\"a}ge, was die Entwicklung und Verbreitung innovativer Dienste beeintr{\"a}chtigt. Derzeitig diskutierte Konzepte wie Software-Defined Networking (SDN) oder Netzvirtualisierung (NV) werden als eine M{\"o}glichkeit angesehen, die Altlasten der bestehenden Internetarchitektur zu l{\"o}sen. Beiden Konzepten gemein ist die Idee, logische Netze {\"u}ber dem physikalischen Substrat zu betreiben. Diese logischen Netze sind hochdynamisch und k{\"o}nnen so flexibel an die Anforderungen der jeweiligen Anwendungen angepasst werden. Insbesondere erlaubt das Konzept der Virtualisierung intelligentere Netzknoten, was innovative neue Anwendungsf{\"a}lle erm{\"o}glicht. Ein h{\"a}ufig in diesem Zusammenhang diskutierter Anwendungsfall ist die Mobilit{\"a}t sowohl von Endger{\"a}ten als auch von Diensten an sich. Die Mobilit{\"a}t der Dienste wird hierbei ausgenutzt, um die Zugriffsverz{\"o}gerung oder die belegten Ressourcen im Netz zu reduzieren, indem die Dienste zum Beispiel in f{\"u}r den Nutzer geographisch nahe Datenzentren migriert werden. Neben den reinen Mechanismen bez{\"u}glich Dienst- und Endger{\"a}temobilit{\"a}t sind in diesem Zusammenhang auch geeignete {\"U}berwachungsl{\"o}sungen relevant, welche die vom Nutzer wahrgenommene Dienstg{\"u}te bewerten k{\"o}nnen. Diese L{\"o}sungen liefern wichtige Entscheidungshilfen f{\"u}r die Migration oder {\"u}berwachen m{\"o}gliche Effekte der Migration auf die erfahrene Dienstg{\"u}te beim Nutzer. Im Falle von Video Streaming erm{\"o}glicht ein solcher Anwendungsfall die flexible Anpassung der Streaming Topologie f{\"u}r mobile Nutzer, um so die Videoqualit{\"a}t unabh{\"a}ngig vom Zugangsnetz aufrechterhalten zu k{\"o}nnen. Im Rahmen dieser Doktorarbeit wird der beschriebene Anwendungsfall am Beispiel einer Video Streaming Anwendung n{\"a}her analysiert und auftretende Herausforderungen werden diskutiert. Des Weiteren werden L{\"o}sungsans{\"a}tze vorgestellt und bez{\"u}glich ihrer Effizienz ausgewertet. Im Detail besch{\"a}ftigt sich die Arbeit mit der Leistungsanalyse von Mechanismen f{\"u}r die Dienstmobilit{\"a}t und entwickelt eine Architektur zur Optimierung der Dienstmobilit{\"a}t. Im Bereich Endger{\"a}temobilit{\"a}t werden Verbesserungen entwickelt, welche die Latenz zwischen Endger{\"a}t und Dienst reduzieren oder die Konnektivit{\"a}t unabh{\"a}ngig vom Zugangsnetz gew{\"a}hrleisten. Im letzten Teilbereich wird eine L{\"o}sung zur {\"U}berwachung der Videoqualit{\"a}t im Netz entwickelt und bez{\"u}glich ihrer Genauigkeit analysiert.}, subject = {Leistungsbewertung}, language = {en} } @phdthesis{Houshiar2017, author = {Houshiar, Hamidreza}, title = {Documentation and mapping with 3D point cloud processing}, isbn = {978-3-945459-14-0}, doi = {10.25972/OPUS-14449}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-144493}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2017}, abstract = {3D point clouds are a de facto standard for 3D documentation and modelling. The advances in laser scanning technology broadens the usability and access to 3D measurement systems. 3D point clouds are used in many disciplines such as robotics, 3D modelling, archeology and surveying. Scanners are able to acquire up to a million of points per second to represent the environment with a dense point cloud. This represents the captured environment with a very high degree of detail. The combination of laser scanning technology with photography adds color information to the point clouds. Thus the environment is represented more realistically. Full 3D models of environments, without any occlusion, require multiple scans. Merging point clouds is a challenging process. This thesis presents methods for point cloud registration based on the panorama images generated from the scans. Image representation of point clouds introduces 2D image processing methods to 3D point clouds. Several projection methods for the generation of panorama maps of point clouds are presented in this thesis. Additionally, methods for point cloud reduction and compression based on the panorama maps are proposed. Due to the large amounts of data generated from the 3D measurement systems these methods are necessary to improve the point cloud processing, transmission and archiving. This thesis introduces point cloud processing methods as a novel framework for the digitisation of archeological excavations. The framework replaces the conventional documentation methods for excavation sites. It employs point clouds for the generation of the digital documentation of an excavation with the help of an archeologist on-site. The 3D point cloud is used not only for data representation but also for analysis and knowledge generation. Finally, this thesis presents an autonomous indoor mobile mapping system. The mapping system focuses on the sensor placement planning method. Capturing a complete environment requires several scans. The sensor placement planning method solves for the minimum required scans to digitise large environments. Combining this method with a navigation system on a mobile robot platform enables it to acquire data fully autonomously. This thesis introduces a novel hole detection method for point clouds to detect obscured parts of a captured environment. The sensor placement planning method selects the next scan position with the most coverage of the obscured environment. This reduces the required number of scans. The navigation system on the robot platform consist of path planning, path following and obstacle avoidance. This guarantees the safe navigation of the mobile robot platform between the scan positions. The sensor placement planning method is designed as a stand alone process that could be used with a mobile robot platform for autonomous mapping of an environment or as an assistant tool for the surveyor on scanning projects.}, subject = {3D Punktwolke}, language = {en} } @phdthesis{Menth2004, author = {Menth, Michael}, title = {Efficient admission control and routing for resilient communication networks}, doi = {10.25972/OPUS-846}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-9949}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2004}, abstract = {This work is subdivided into two main areas: resilient admission control and resilient routing. The work gives an overview of the state of the art of quality of service mechanisms in communication networks and proposes a categorization of admission control (AC) methods. These approaches are investigated regarding performance, more precisely, regarding the potential resource utilization by dimensioning the capacity for a network with a given topology, traffic matrix, and a required flow blocking probability. In case of a failure, the affected traffic is rerouted over backup paths which increases the traffic rate on the respective links. To guarantee the effectiveness of admission control also in failure scenarios, the increased traffic rate must be taken into account for capacity dimensioning and leads to resilient AC. Capacity dimensioning is not feasible for existing networks with already given link capacities. For the application of resilient NAC in this case, the size of distributed AC budgets must be adapted according to the traffic matrix in such a way that the maximum blocking probability for all flows is minimized and that the capacity of all links is not exceeded by the admissible traffic rate in any failure scenario. Several algorithms for the solution of that problem are presented and compared regarding their efficiency and fairness. A prototype for resilient AC was implemented in the laboratories of Siemens AG in Munich within the scope of the project KING. Resilience requires additional capacity on the backup paths for failure scenarios. The amount of this backup capacity depends on the routing and can be minimized by routing optimization. New protection switching mechanisms are presented that deviate the traffic quickly around outage locations. They are simple and can be implemented, e.g, by MPLS technology. The Self-Protecting Multi-Path (SPM) is a multi-path consisting of disjoint partial paths. The traffic is distributed over all faultless partial paths according to an optimized load balancing function both in the working case and in failure scenarios. Performance studies show that the network topology and the traffic matrix also influence the amount of required backup capacity significantly. The example of the COST-239 network illustrates that conventional shortest path routing may need 50\% more capacity than the optimized SPM if all single link and node failures are protected.}, subject = {Kommunikation}, language = {en} } @phdthesis{Niebler2019, author = {Niebler, Thomas}, title = {Extracting and Learning Semantics from Social Web Data}, doi = {10.25972/OPUS-17866}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178666}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {Making machines understand natural language is a dream of mankind that existed since a very long time. Early attempts at programming machines to converse with humans in a supposedly intelligent way with humans relied on phrase lists and simple keyword matching. However, such approaches cannot provide semantically adequate answers, as they do not consider the specific meaning of the conversation. Thus, if we want to enable machines to actually understand language, we need to be able to access semantically relevant background knowledge. For this, it is possible to query so-called ontologies, which are large networks containing knowledge about real-world entities and their semantic relations. However, creating such ontologies is a tedious task, as often extensive expert knowledge is required. Thus, we need to find ways to automatically construct and update ontologies that fit human intuition of semantics and semantic relations. More specifically, we need to determine semantic entities and find relations between them. While this is usually done on large corpora of unstructured text, previous work has shown that we can at least facilitate the first issue of extracting entities by considering special data such as tagging data or human navigational paths. Here, we do not need to detect the actual semantic entities, as they are already provided because of the way those data are collected. Thus we can mainly focus on the problem of assessing the degree of semantic relatedness between tags or web pages. However, there exist several issues which need to be overcome, if we want to approximate human intuition of semantic relatedness. For this, it is necessary to represent words and concepts in a way that allows easy and highly precise semantic characterization. This also largely depends on the quality of data from which these representations are constructed. In this thesis, we extract semantic information from both tagging data created by users of social tagging systems and human navigation data in different semantic-driven social web systems. Our main goal is to construct high quality and robust vector representations of words which can the be used to measure the relatedness of semantic concepts. First, we show that navigation in the social media systems Wikipedia and BibSonomy is driven by a semantic component. After this, we discuss and extend methods to model the semantic information in tagging data as low-dimensional vectors. Furthermore, we show that tagging pragmatics influences different facets of tagging semantics. We then investigate the usefulness of human navigational paths in several different settings on Wikipedia and BibSonomy for measuring semantic relatedness. Finally, we propose a metric-learning based algorithm in adapt pre-trained word embeddings to datasets containing human judgment of semantic relatedness. This work contributes to the field of studying semantic relatedness between words by proposing methods to extract semantic relatedness from web navigation, learn highquality and low-dimensional word representations from tagging data, and to learn semantic relatedness from any kind of vector representation by exploiting human feedback. Applications first and foremest lie in ontology learning for the Semantic Web, but also semantic search or query expansion.}, subject = {Semantik}, language = {en} } @phdthesis{Budig2018, author = {Budig, Benedikt}, title = {Extracting Spatial Information from Historical Maps: Algorithms and Interaction}, edition = {1. Auflage}, publisher = {W{\"u}rzburg University Press}, address = {W{\"u}rzburg}, isbn = {978-3-95826-092-4}, doi = {10.25972/WUP-978-3-95826-093-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-160955}, school = {W{\"u}rzburg University Press}, pages = {viii, 160}, year = {2018}, abstract = {Historical maps are fascinating documents and a valuable source of information for scientists of various disciplines. Many of these maps are available as scanned bitmap images, but in order to make them searchable in useful ways, a structured representation of the contained information is desirable. This book deals with the extraction of spatial information from historical maps. This cannot be expected to be solved fully automatically (since it involves difficult semantics), but is also too tedious to be done manually at scale. The methodology used in this book combines the strengths of both computers and humans: it describes efficient algorithms to largely automate information extraction tasks and pairs these algorithms with smart user interactions to handle what is not understood by the algorithm. The effectiveness of this approach is shown for various kinds of spatial documents from the 16th to the early 20th century.}, subject = {Karte}, language = {en} } @phdthesis{Glasser2001, author = {Glaßer, Christian}, title = {Forbidden-Patterns and Word Extensions for Concatenation Hierarchies}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-1179153}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2001}, abstract = {Starfree regular languages can be build up from alphabet letters by using only Boolean operations and concatenation. The complexity of these languages can be measured with the so-called dot-depth. This measure leads to concatenation hierarchies like the dot-depth hierarchy (DDH) and the closely related Straubing-Th{\´e}rien hierarchy (STH). The question whether the single levels of these hierarchies are decidable is still open and is known as the dot-depth problem. In this thesis we prove/reprove the decidability of some lower levels of both hierarchies. More precisely, we characterize these levels in terms of patterns in finite automata (subgraphs in the transition graph) that are not allowed. Therefore, such characterizations are called forbidden-pattern characterizations. The main results of the thesis are as follows: forbidden-pattern characterization for level 3/2 of the DDH (this implies the decidability of this level) decidability of the Boolean hierarchy over level 1/2 of the DDH definition of decidable hierarchies having close relations to the DDH and STH Moreover, we prove/reprove the decidability of the levels 1/2 and 3/2 of both hierarchies in terms of forbidden-pattern characterizations. We show the decidability of the Boolean hierarchies over level 1/2 of the DDH and over level 1/2 of the STH. A technique which uses word extensions plays the central role in the proofs of these results. With this technique it is possible to treat the levels 1/2 and 3/2 of both hierarchies in a uniform way. Furthermore, it can be used to prove the decidability of the mentioned Boolean hierarchies. Among other things we provide a combinatorial tool that allows to partition words of arbitrary length into factors of bounded length such that every second factor u leads to a loop with label u in a given finite automaton.}, subject = {Automatentheorie}, language = {en} } @phdthesis{Reith2001, author = {Reith, Steffen}, title = {Generalized Satisfiability Problems}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-74}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2001}, abstract = {In the last 40 years, complexity theory has grown to a rich and powerful field in theoretical computer science. The main task of complexity theory is the classification of problems with respect to their consumption of resources (e.g., running time or required memory). To study the computational complexity (i.e., consumption of resources) of problems, similar problems are grouped into so called complexity classes. During the systematic study of numerous problems of practical relevance, no efficient algorithm for a great number of studied problems was found. Moreover, it was unclear whether such algorithms exist. A major breakthrough in this situation was the introduction of the complexity classes P and NP and the identification of hardest problems in NP. These hardest problems of NP are nowadays known as NP-complete problems. One prominent example of an NP-complete problem is the satisfiability problem of propositional formulas (SAT). Here we get a propositional formula as an input and it must be decided whether an assignment for the propositional variables exists, such that this assignment satisfies the given formula. The intensive study of NP led to numerous related classes, e.g., the classes of the polynomial-time hierarchy PH, P, \#P, PP, NL, L and \#L. During the study of these classes, problems related to propositional formulas were often identified to be complete problems for these classes. Hence some questions arise: Why is SAT so hard to solve? Are there modifications of SAT which are complete for other well-known complexity classes? In the context of these questions a result by E. Post is extremely useful. He identified and characterized all classes of Boolean functions being closed under superposition. It is possible to study problems which are connected to generalized propositional logic by using this result, which was done in this thesis. Hence, many different problems connected to propositional logic were studied and classified with respect to their computational complexity, clearing the borderline between easy and hard problems.}, subject = {Erf{\"u}llbarkeitsproblem}, language = {en} }