Epistemic Reasoning in OWL 2 DL

The standard semantics employed for description logics (DLs) adheres to the open world assumption (OWA). On one hand, such an assumption facilitates a modeler to formally represent problem domains with out explicitly expressing full information, which sometimes is even not possible. This is probably one of the main reasons of founding the Web Ontology Language (OWL) based on DLs. On the other hand, OWA proves to be the main cause of the impotence of DLs of capturing non-monotonic reasoning: where new information invalidates the previously concluded information. Non-monotonic reasoning has several applications in real life scenarios. For example, logic programming community, parallel to the OWL community, in general focuses on non-monotonic reasoning. These short-comes of DLs lead to the quest for a formalism as suitable as DLs meanwhile capable of capturing some “kind” of non-monotonic reasoning. Several work has been done on extending DLs with some non-monotonic feature. Epistemic extensions of DLs (called epistemic DLs sometimes) is probably one of the earliest work in this direction. Such extensions enhance expressivity and querying capabilities of these DLs by knowledge base introspection. The existing approaches in this respect are limited to less expressive DLs like ALC: the least expressive DL which is boolean complete whereas in real life applications, modeling problems require expressivity beyond ALC. The aim of this work is to extend epistemically the most expressive DL SROIQ which is the foundation of OWL 2 DL. We argue that unintended effects occur when imposing the semantics traditionally employed on very expressive DLs like SROIQ. Consequently, we identify the most expressive DL for which the current approach can still be adapted. For the epistemic extension of SROIQ and alike expressive DLs, we suggest a revised semantics that behaves more intuitively in these cases and coincides with the traditional semantics on less expressive DLs.