Alena Lukasová

Reasoning in RDF graphic formal system with quantifiers

Both associative networks and RDF model (here we consider especially its graph version) belong to formal systems of knowledge representation based on concept-oriented paradigm. To treat properties of both of them as common properties of the systems is therefore natural. The article shows a possibility to use universal and existential quantified statements introduced prior to associative networks also within RDF graphic system and to define a RDF formal system with extended syntax and semantic that can use inference rules of associative networks. As an example solution, a logical puzzle is presented.

Knowledge represented using RDF semantic network in the concept of semantic web

The RDF(S) model has been declared as the basic model to capture knowledge of the semantic web. It provides a common and flexible way to decompose composed knowledge to elementary statements, which can be represented by RDF triples or by RDF graph vectors. From the logical point of view, elements of knowledge can be expressed using at most binary predicates, which can be converted to RDF-triples or graph vectors. However, it is not able to capture implicit knowledge representable by logical formulas. This contribution shows how existing approaches (semantic networks and clausal form logic) can be combined together with RDF to obtain RDF-compatible system with ability to represent implicit knowledge and inference over knowledge base.

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.

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.