Martin Žáček

Visualization of Semantic Data

The main goal of the Semantic Web is to direct the current syntactic web on the path to the Semantic Web. The vision of the Semantic Web is to interpret information on the web to be readable and machine-interpretable. Therefore, the article focuses on the creation of an instrument for visualizing semantic data on the basis of the identified advantages and disadvantages of existing applications for visualization, which are currently available.

Building a Non-monotonic Default Theory in GCFL Graph-Version of RDF

The aim describes the idea of graph-based representation of clauses. This approach follows the Richards idea of graph-based clausal form knowledge representation. Moreover, it enabled to build up the graph-based formal system GCFL (Graph-based Clausal Form Logic) that cannot only illustrate knowledge bases graphically, but also allows us to obtain consequents of a knowledge base in a special graph-based way. The article continues the idea by creation of a graph-based formal system of generating revisable theories following the known Reiter’s default principle of building non-monotonic theories.

Knowledge bases built on web languages from the point of view of predicate logics

The article undergoes evaluation of formal systems created on the base of web (ontology/concept) languages by simplifying the usual approach of knowledge representation within the FOPL, but sharing its expressiveness, semantic correct-ness, completeness and decidability. Evaluation of two of them – that one based on description logic and that one built on RDF model principles - identifies some of the lacks of those formal systems and presents, if possible, corrections of them. Possibilities to build an inference system capable to obtain new further knowledge over given knowledge bases including those describing domains by giant linked domain databases has been taken into account. Moreover, the directions towards simplifying FOPL language discussed here has been evaluated from the point of view of a possibility to become a web language for fulfilling an idea of semantic web.

Reasoning in Formal Systems of Extended RDF Networks

It is a fact that the RDF(S) model has been declared as the ground base for implementations of further web development conception. RDF provides a common and flexible way to decompose knowledge to elementary statements that allows, as networks of indivisible knowledge atoms, to be represented by RDF triples or by RDF graph vectors.

Carstairs-McCarthy’s Morphological Rules of English Language in RDFCFL Graphs

The article presents an approach to express morphology and syntax rules or specifications of basic terminology of the English language in RDFCFL graphic metalanguage following the methodology of Andrew Carstairs-McCarthy’s book. The formal modelling of English linguistics follows here two levels: syntactical (investigating lexical and functional categories of speech, in particular rules of their merging into larger units) and semantic-based morphology of the English language which covers the importance of language morphemes.

RDF graph-based formal system in relation to the Sowa’s conceptual graph

RDF model and Sowovy conceptual graphs are two different directions, although are based on the associative (semantic) networks. This article is a build on the author’s work concerning the modified RDF graph-based model, which has a higher expressiveness. This article aims to start work on both formal systems and find common features for conversion. The reason this work is RDF, which is a data format designed to enable semantic interoperability between computers, and the largest part of its specification provides the means for this in defining the core vocabulary, an XML serialization, inferencing, etc.

Ontology Languages for Semantic Web from a Bit Higher Level of Generality

An article tries to see a group of semantic web representation and communication means like description logics, semantic networks, RDF model and language, OWL language, RDF CFL etc. taking a part at the development of formal ontologies from a slightly higher (meta) level. A focus has been oriented towards properties that semantic web language ought to have to fulfill according to a semantic web idea. Consequently the article tries to draw by the help of the means above the trip towards a proper semantic-web ontology language fulfilling the main demands of expressivity and also easy-to-use conditions. Even if the development of a semantic web language was until now much more complicated with a taking part of a lot of people or companies the authors of the article try to contribute to an analyzing of the actual state by drawing it as a cloud of demands, streams, events or condition’s fulfilling that at the end would have brought into the world an easy-to-usable semantic web ontology language having all the demands fulfilled. The article moreover shows that a language RDF CFL belongs nowadays to the semantic web family as a unique well usable tool of reasoning within semantic web knowledge bases.

Making a Shift from Believing to Knowing by the Help of RDF CFL Formal Representation

In the frame of seeking an optimal formal language means for semantic web inferences a model and language RDF CFL has been developed. Using an intensional approach to the language semantics in its graph-based style of representation a demand of open world has been fulfilled. On the other side the RDF CFL system contains a package of inference methods working especially in closed-worlds, that have been developed in the clausal form of first order predicate logics, useful for solving a lot of tasks over corresponding knowledge bases. The article shows one of the capabilities of our RDF CFL graph language using as an example a well-known Castaněda’s puzzle that has been before used by some authors of new formal approaches, like for example Shapiro’s SNaPS for testing their possibilities. The believing versus knowing problem accompanying the puzzle brings into a discussion a further dimension.

Knowledge formalization of intelligent building

This article aim is understanding the basic knowledge about an intelligent building. The notion of the intelligent building can be called any building equipped with computer and communication technology, which can automatically respond to internal or external stimuli. The result of the intelligent building is an automated and foreseeing of activities that enable to reduce operating costs and increase comfort. The best way to use the intelligent building is for a low-energy building, a passive building, or for building with high savings. The output of this article is the formalization of basic knowledge of the intelligent building by RDF graph.