Determining source contribution in integration systems

Owners of sources registered in an information integration system, which provides answers to a (potentially evolving) set of client queries, need to know their contribution to the query results. We study the problem of deciding, given a client query Q and a source registration R, whether R is (i) “self-sufficient ” (can contribute to the result of Q even if it is the only source in the system) or (ii) “now complementary ” (can contribute, but only in cooperation with other specific existing sources), or (iii)“later complementary ” (can contribute if in the future appropriate new sources join the system). We consider open-world integration systems in which registrations are expressed using source-to-target constraints, and queries are answered under “certain answer ” semantics. 1