Mark Kaminski

Learn More
This thesis presents Spartacus, a tableau-based reasoner for hybrid logic with global modalities and reflexive and transitive relations. To obtain termination in the presence of global modalities and transitive relations, Spartacus uses pattern-based blocking. To achieve a competitive performance on practical problems, we employ a range of optimization(More)
This paper contributes to the principled construction of terminating tableau systems for modal logic with nominals and difference modalities [4, 1, 8, 11]. We also consider global and converse modalities and reflexive and transitive relations. Nominals and difference enrich modal logic with equational constraints, and handling these constraints in a(More)
We present a terminating tableau calculus for graded hybrid logic with global modalities, reflexivity, transitivity and role hierarchies. Termination of the system is achieved through pattern-based blocking. Previous approaches to related logics all rely on chain-based blocking. Besides being conceptually simple and suitable for efficient implementation,(More)
Answering conjunctive queries over ontology-enriched datasets is a core reasoning task for many applications. Query answering is, however, computationally very expensive, which has led to the development of query answering procedures that sacrifice either expressive power of the ontology language, or the completeness of query answers in order to improve(More)
We study the problem of answering instance queries over non-Horn ontologies by rewriting them into Datalog programs or FirstOrder queries (FOQs). We consider the basic non-Horn language ELU , which extends EL with disjunctions. Both Datalog-rewritability and FOrewritability of instance queries have been recently shown to be decidable for ALC ontologies (and(More)
Module extraction—the task of computing a (preferably small) fragment M of an ontology T that preserves entailments over a signature Σ—has found many applications in recent years. Extracting modules of minimal size is, however, computationally hard, and often algorithmically infeasible. Thus, practical techniques are based on approximations, where M(More)
As life expectancy increases, so do the problems of the elderly population. One major problem is that of protein calorie malnutrition; another is the susceptibility of this population to pressure sores. The purpose of this study was to determine if a correlation exists between deteriorating nutritional status and the development of pressure sores. The(More)
We study the closely related problems of rewriting disjunctive datalog programs and non-Horn DL ontologies into plain datalog programs that entail the same facts for every dataset. We first propose the class of markable disjunctive datalog programs, which is efficiently recognisable and admits polynomial rewritings into datalog. Markability naturally(More)
We present the first goal-directed decision procedure for hybrid PDL. The procedure is based on a modular approach that scales from basic modal logic with eventualities to hybrid PDL. The approach is designed so that nominals and eventualities are treated orthogonally. To deal with the complex programs of PDL, the approach employs a novel disjunctive(More)