A set-theoretic interpretation of the relational model was proposed by Spyratos and Lecluse [17]. It is also contended [16] that multivalued dependencies (mvd) can be treated as inference rules. In this paper multivalued dependencies are treated as inference rules rather than as integrity constraints, and an Extended Query Model for deductive query answering is given. The Extended Query Model is considered as an extension of the Query Model [18] because it also includes multivalued dependencies treated as inference rules. The old query model considers only functional dependencies. They are analyzed to establish how they affect query processing in relational databases.