Abstract
Consistent query answering over description logic based ontologies is an important topic in ontology engineering as it can provide meaningful answers to queries posed over inconsistent ontologies. Current approaches for dealing with this problem usually consist of two steps: the first one is to extract some consistent sub-ontologies of an inconsistent ontology, and then the second one is to pose the query over these consistent sub-ontologies. In this paper, we propose an alternative approach to consistent query answering for conjunctive queries over DL-Lite ontologies based on four-valued semantics, where DL-Lite is a family of tractable Description Logics (DLs). We give an algorithm to compute answers to a query over an inconsistent DL-Lite ontology and show that it is tractable. In particular, we show that it is in PTime with respect to the size of the TBox, and is LOGSPACE with respect to the size of the ABox.