tailieunhanh - Semantic Web Technologies phần 4

nơi mà các khái niệm tương ứng với chủ đề và các tài liệu có liên quan đến các chủ đề này thông qua một mối quan hệ thích hợp, chẳng hạn như hasSubject (Grobelnik và Mladenic 2005a), | SYNTACTIC RELEVANCE-BASED SELECTION FUNCTIONS 85 SYNTACTIC RELEVANCE-BASED SELECTION FUNCTIONS As we have pointed out in Section the definition of the selection function should be independent of the general procedure of the inconsistency processing . strategy . Further research will focus on a formal development of selection functions. However we would like to point out that there exist several alternatives which can be used for an inconsistency reasoner. Chopra et al. 2000 propose syntactic relevance to measure the relationship between two formulas in belief sets so that the relevance can be used to guide the belief revision based on Schaerf and Cadoli s method of approximate reasoning. We will exploit their relevance measure as selection function and illustrate them on two examples. Definition 9 Direct Relevance and k-Relevance Chopra et al. 2000 . Given a formula set s two atoms p q are directly relevant denoted by R p q S if there is a formula a 2 such that p q appear in a. A pair of atoms p and q are k-relevant with respect to if there exist p1 p2 pk 2 L such that p p1 are directly relevant pi pi 1 are directly relevant i 1 k 1 pk q are directly relevant. The notions of relevance are based on propositional logics. However ontology languages are usually written in some subset of first order logic. It would not be too difficult to extend the ideas of relevance to those first-order logic-based languages by considering an atomic formula in first-order logic as a primitive proposition in propositional logic. Given a formula f we use I f C f R f to denote the sets of individual names concept names and relation names that appear in the formula f respectively. Definition 10 Direct Relevance . Two formula f and c are directly relevant if there is a common name which appears both in formula f and formula c that is Iff I C 0 V C f C C 0 V R f R C 0. Definition 11 Direct Relevance to a Set . A formula f is relevant to a set of formula if there exists a formula