In this paper, we present an approach to query processing for paraconsistent databases in the presence of integrity constraints. Paraconsistent databases are capable of representing positive as well as negative facts and typically operate under the open world assumption. It is easily observed that integrity constraints are usually statements about negative facts and as a result paraconsistent databases are suitable as a representation mechanism for such information. We use set-valued attributes to code large number of regular tuples into one extended tuple (with set-valued components). We define an extended relational model and algebra capable of representing and querying paraconsistent databases in the presence of integrity constraints. The extended algebra is used as the basis for query processing in such databases.