A general framework for query answering in data quality-based Cooperative Information Systems

Data quality in Cooperative Information Systems (CISs) which integrate a number of local heterogeneous database systems is an increasingly important issue. Current in-practice developed CISs are based on different software and architectural paradigms, and are specified a number of ad-hoc algorithms for quality query-answering, without an unifying logic framework (differently from well defined semantics in data integration systems). The consequence is that each software system responds in some way to user queries with record for which is not often clear if it is really a logic answer from CISs database. Sometimes it is not also clear if the records obtained are complete answers w.r.t. the logically derivable answers from the system. Because of such considerations, in this paper we present a general framework for a query-answering in a logic theory in Data Quality Cooperative Information Systems (DaQuinCIS), by an epistemic extension of the standard data integration systems, and we introduce also a 4-valued logic in order to deal with incomplete and inconsistent information.