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Blocking mechanisms in description logics, a general approach

Dmitry Tishkovsky - 11.6.2008

We will take a close look on various standard mechanism of blocking in tableaux for various description logics and attemt to simulate these mechanisms by a general blocking rule - the unrestricted blocking rule. In particular, we will consider static and dynamic, subset and equality, and successor and anywhere blocking mechanisms.


A General Tableau Method for Deciding Description Logics, Modal Logics and Related First-Order Fragments

Dmitry Tishkovsky - 11.6.2008

A general method for proving termination of tableaux-based procedures for modal-type logics and related first-order fragments will be presented. The method is based on connections between filtration arguments and a general blocking technique. The method provides a general framework for developing tableau-based decision procedures for a large class of logics. In particular, the method can be applied to many well-known description and modal logics. The class includes traditional modal logics such as S4 and modal logics with the universal modality, as well as description logics such as ALC with nominals and general TBoxes. Also contained in the class are harder and less well-studied modal logics with complex modalities and description logics with complex role operators such as Boolean modal logic, and the description logic ALBO. In addition, the techniques allow us to specify tableau-based decision procedures for related solvable fragments of first-order logic, including the two-variable fragment of first-order logic. This solves a long-standing open problem.


Reasoning about actions and knowlege: Multi-agent dynamic logics with informational test

Dmitry Tishkovsky - 9.6.2008

The logics are based on a new formalisation and semantics of the test operator of propositional dynamic logic and a representation of actions which distinguishes abstract actions from concrete actions. The new test operator, called informational test, can be used to formalise the beliefs and knowledge of particular agents as dynamic modalities. This approach is consistent with the formalisation of the agents` beliefs and knowledge as K(D)45 and S5 modalities. Properties concerning informativeness, truthfulness and preservation of beliefs were proved for a derivative of the informational test operator. It was shown that common belief and common knowledge can be expressed in the considered logics. This means, the logics are more expressive than propositional dynamic logic with an extra modality for belief or knowledge. The logics remain decidable and belong to 2EXPTIME. Versions of the considered logics express natural additional properties of beliefs or knowledge and interaction of beliefs or knowledge with actions. It was shown that a simulation of PDL can be constructed in one of these extensions.

Internal information

Official Project Informations
Project name:

Intelligent Models, Algorithms, Methods and Tools for the Semantic Web (realization), of the Program "Information Society" (of the Thematic Program II of the National Program of Research in the Czech Republic).

Project code:


Paper project quotation:

The work was supported by the project 1ET100300419 of the Program Information Society (of the Thematic Program II of the National Research Program of the Czech Republic) "Intelligent Models, Algorithms, Methods and Tools for the Semantic Web Realisation".



Useful links

Project links:

OLE Ontology Acquisition Project - a part of Brno project result, namely Vit Novacek's part

Other projects:

MSTeP - Modeling and simulation of complex technical problems: effective numerical algorithms and parallel implementation using new information technologies

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