FACULTÉ & RECHERCHE

Consistent query answering (CQA) is an inconsistency tolerant approach to obtaining semantically correct answers from a database that may be inconsistent with respect to a set of integrity constraints. In this work, we formalize the notion of consistent query answer for spatial databases with respect to a special but relevant class of spatial semantic integrity constraints (SICs). In order to do this, we first characterize conflicting spatial data, and next, define admissible instances that restore consistency while staying close to the original instance. In this way we obtain a repair semantics, which is used as an instrumental concept to define consistent answers as a set-theoretic and geometric aggregation of answers from all admissible repairs. After establishing the intractability of consistent query answering, we identify and investigate a class of denial SICs (IDSICs) and spatial queries for which it is possible to efficiently compute consistent query answers via core computation.