Understanding Inexpressibility of Model−Based ABox Evolution in DL−Lite

Abstract

International audienceEvolution of Knowledge Bases (KBs) expressed in Description Logics (DLs) proved its importance. Recent studies of evolution in DLs mostly focussed on model-based approaches. They showed that evolution of KBs in tractable DLs, such as DL-Lite, suffers from inexpressibility, i.e., the result of evolution cannot be captured in DL-Lite. What is missing in these studies is understanding: in which DL-Lite fragments evolution can be captured, what causes the inexpressibility, which logics is sufficient to express evolution, and whether one can approximate it in DL-Lite. This paper provides some understanding of these issues for both update and revision. We found what DL-Lite formulas make evolution inexpressible and how to capture evolution in their absence. We introduce the notion of prototypes that gives an understanding of how to capture evolution for a rich DL-Lite fragment in FO[2]. Decidability of FO[2] gives possibility for approximations