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Extrakce informací z webových stránek pomoci extrakčních ontologií
Labský, Martin ; Berka, Petr (advisor) ; Strossa, Petr (referee) ; Vojtáš, Peter (referee) ; Snášel, Václav (referee)
Automatic information extraction (IE) from various types of text became very popular during the last decade. Owing to information overload, there are many practical applications that can utilize semantically labelled data extracted from textual sources like the Internet, emails, intranet documents and even conventional sources like newspaper and magazines. Applications of IE exist in many areas of computer science: information retrieval systems, question answering or website quality assessment. This work focuses on developing IE methods and tools that are particularly suited to extraction from semi-structured documents such as web pages and to situations where available training data is limited. The main contribution of this thesis is the proposed approach of extended extraction ontologies. It attempts to combine extraction evidence from three distinct sources: (1) manually specified extraction knowledge, (2) existing training data and (3) formatting regularities that are often present in online documents. The underlying hypothesis is that using extraction evidence of all three types by the extraction algorithm can help improve its extraction accuracy and robustness. The motivation for this work has been the lack of described methods and tools that would exploit these extraction evidence types at the same time. This thesis first describes a statistically trained approach to IE based on Hidden Markov Models which integrates with a picture classification algorithm in order to extract product offers from the Internet, including textual items as well as images. This approach is evaluated using a bicycle sale domain. Several methods of image classification using various feature sets are described and evaluated as well. These trained approaches are then integrated in the proposed novel approach of extended extraction ontologies, which builds on top of the work of Embley [21] by exploiting manual, trained and formatting types of extraction evidence at the same time. The intended benefit of using extraction ontologies is a quick development of a functional IE prototype, its smooth transition to deployed IE application and the possibility to leverage the use of each of the three extraction evidence types. Also, since extraction ontologies are typically developed by adapting suitable domain ontologies and the ontology remains in center of the extraction process, the work related to the conversion of extracted results back to a domain ontology or schema is minimized. The described approach is evaluated using several distinct real-world datasets.
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Mapování ontologií a jeho vyhodnocování pomocí vzorů
Zamazal, Ondřej ; Svátek, Vojtěch (advisor) ; Vacura, Miroslav (referee) ; Pokorný, Jaroslav (referee) ; Štuller, Július (referee)
Ontology Matching is one of the hottest topic within the Semantic Web of recent years. There is still ample of space for improvement in terms of performance. Furthermore, current ontology matchers mostly concentrate on simple entity to entity matching. However, matching of whole structures could bring some additional complex relationships. These structures of ontologies can be captured as ontology patterns. The main theme of this thesis is an examination of pattern-based ontology matching enhanced with ontology transformation and pattern-based ontology alignment evaluation. The former is examined due to its potential benefits regarding complex matching and matching as such. The latter is examined because complex hypotheses could be beneficial feedback as complement to traditional evaluation methods. These two tasks are related to four different topics: ontology patterns, ontology transformation, ontology alignment evaluation and ontology matching. With regard to those four topics, this work covers the following aspects: * Examination of different aspects of ontology patterns. Particularly, description of relevant ontology patterns for ontology transformation and for ontology matching (such as naming, matching and transformation patterns). * Description of a pattern-based method for ontology transformation. * Introduction of new methods for an alignment evaluation; including using patterns as a complex structures for more detailed analysis. * Experiments and demonstrations of new concepts introduced in this thesis. The thesis first introduces naming pattern and matching pattern classification on which ontology transformation framework is based. Naming patterns are useful for detection of ontology patterns and for generation of new names for entities. Matching patterns are basis for transformation patterns in terms of sharing some building blocks. In comparison with matching patterns, transformation patterns have transformation links that represent way how parts of ontology patterns are transformed. Besides several evaluations and implementations, the thesis provides a demonstration of getting complex matching due to ontology transformation process. Ontology transformation framework has been implemented in Java environment where all generic patterns are represented as corresponding Java objects. Three main implemented services are made generally available as RESTful services: ontology pattern detection, transformation instruction generation and ontology transformation.
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SPARQL plugin for Ontopia Knowledge Suite
Ovčáčík, Vlastimil ; Kliegr, Tomáš (advisor) ; Svátek, Vojtěch (referee)
Reader of this bachelor thesis will familiarize with two technologies of semantic web -- Topic Maps and RDF. In the first half of this document we can find principles, history and thoughts on near future of both technologies. There are explained necessary principles of both standards. Emphasis is placed on query languages SPARQL and TMQL. Object of this thesis is understanding differences and mutual aspects of both Topic Maps and RDF. This understanding is key for finding interoperability between these two technologies on semantic web. The second half of this thesis is aimed on implementation of sparql4ontopia - a plugin for Ontopia Knowledge Suite, which enables quering topic maps with SPARQL. This plugin utilizes Sesame project for SPARQL query evaluation and Nikunau tool from SesameTM project for mapping SPARQL on Topic Maps Data Model. Possibilities and limitations of this plugin are described. There is also description of sparql4ontopia development and implementation. Last chapter shed light on SPARQL endpoint and possible way of implementation into Ontopia Knowledge Suite.
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Ontology Transformation Pattern Editor
Dudáš, Marek ; Zamazal, Ondřej (advisor) ; Vacura, Miroslav (referee)
In lifecycle of ontologies -- during their creation, extension and various ways of their usage there may arise a need for changing the current modeling style of the ontology -- for transforming the ontology. Such transformation may be of course done manually, but in case of larger ontologies the process can be quite time consuming and even when transforming smaller ontologies there is a risk of making mistakes. In [1] a collection of software services and framework for automatic or semiautomatic ontology transformation has been introduced. The input for these services is (together with the source ontology which we want to transform) a definition of the transformation called a transformation pattern in a form of an XML (so basically a text) file. As a topic of this bachelor's work I created a Graphical editor of transformation patterns (TP Editor) -- an application that allows creation of transformation patterns in a similar way as UML modeling tools makes software design easier. The application has form of a plugin for Eclipse. This work contains a short introduction into the domain of transformation patterns, a user guide for the plugin and a programmer's guide. The programmers guide contains an introduction into used technology -- the GEF library, description of the source code and suggestions for further development of the plugin.
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Web interface for ontology similarity measures
Pichl, Ota ; Zamazal, Ondřej (advisor) ; Svátek, Vojtěch (referee)
Semantic Web is one of the most recent topics on the internet. The idea of Semantic Web is associated to informatics ontologies which can provide features for description of web knowledge. Ontologies than bring the feature of semantic annotation for data and knowledge on the internet. This work is focused on comparison of ontologies and determination of their similarity or dissimilarity. Determination of these similarities can be made with various types of methods like vector space measures or collection measures. It is appropriate to implement these methods due to problems and uncertainties which ontologies can bring. Ontology independence is one of the basic characteristics (open world assumption) and because of independence there can appear certain conflicts if exist two ontologies describing the same part of reality. There can be a problem when these two ontologies describe the same entity but with different label or in different structure. Nevertheless there are many other reasons for making these comparisons e.g. extension of semantic search engines or searching for similar ontologies which could be joined together. Solution of this problem can be found in ontology similarity measures. Currently there is no application like this which would provide methods for ontology measures. The main goal of this bachelor thesis is to create a web interface which will provide essential methods for determination of ontology similarity.
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Ontologies represented in a relational database
Lučkaničová, Jekaterina ; Chlapek, Dušan (advisor) ; Tomášková, Barbora (referee)
Searching on the internet is still moving forward. The reason is very simple, more and more people use the internet to fint information, but they are often not satisfied with results. Growing body of information that requires large repositories of knowledge. Because of growing number of information stored in repositories , it is harder to get the resources you need. This work was created on the basic of knowledge about the semantic web. It seeks to familiarizethe general public about ontology, which contents the meanings of words and allows the use of these technologies. The work has a practical part in which the proposal as an ontological storage sites, as well as a repository built on a relational database.
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Modelování podnikových procesů
Panuška, Martin ; Řepa, Václav (advisor) ; Svatoš, Oleg (referee)
In the master's thesis we are concerned with the logical perspective on business process model-ing. The logical perspective on business process modeling has several advantages. First, being a formal logical system, first-order logic let us thoroughly understand the foundations of process modeling. Second, after we understand the logical foundations of business process modeling, we are free to build a BPM language based entirely on logic, or map an existing language onto logic, which may be useful for artificial reasoning. Third, if the business process model is mapped to logic (or another declarative language) it can be easily stored in a declarative knowledge base. Forth, logic based process models can be used in companies as a basis for knowledge manage-ment. And fifth, the science of logic offers a number of various semantic enhancements, which can be used in favor of better business process modeling expressiveness. The first objective of the thesis is to perform a thorough review of the literature of both our fields -- the business process modeling and temporal logic. The related second objective is to study the ability of logic to represent processes and the notion of time in general, and to offer techniques for logical process representation. Subsequently, the examples should be provided in order to present that the selected techniques are capable of performing what is sketched in the first paragraph. The third objective is to propose improvements of the current business process modeling approach and provide relevant examples. Eventually, means of extending the tech-niques presented can be proposed, too. The major contribution of the thesis is that it constitutes a reasonable basis for further research in the chosen field. For novices or even experienced in the subject it represents a good stepping stone.
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Ontology-Driven Self-Organization of Politically Engaged Social Groups
Belák, Václav ; Svátek, Vojtěch (advisor) ; Nováček, Vít (referee)
This thesis deals with the use of knowledge technologies in support of self-organization of people with joint political goals. It first provides a theoretical background for a development of a social-semantic system intended to support self-organization and then it applies this background in the development of a core ontology and algorithms for support of self-organization of people. It also presents a design and implementation of a proof-of-concept social-semantic web application that has been built to test our research. The application stores all data in an RDF store and represents them using the core ontology. Descriptions of content are disambiguated using the WordNet thesaurus. Emerging politically engaged groups can establish themselves into local political initiatives, NGOs, or even new political parties. Therefore, the system may help people easily participate on solutions of issues which are influencing them.
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