Strongly-coupled semantic data integration in P2P settings
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In a peer-to-peer data integration system each peer exposes a schema,
and can map other peers' data on its own schema. Queries are posed
against these local schemata, that means that, comparing with the
usual data integration setting, there is no global schema. This poses
new interesting problems, as the usual data integration semantics,
based on first-order logic, gives rise to undecidability in query
answering even of conjunctive queries. Some have proposed limitations
to the mappings topology (acyclicity), or to the completeness of the
certain answers retrieved. Others are investigating new semantics for
the mapping concept in a peer to peer setting, in order to capture the
expressiveness that we expect from data integration, maintaining the
decidability of query answering. In this talk I will present one of
these approaches, from the theoretical background to the design of a
sound and complete query answering algorithm. Other approaches and
possible development are also addressed in a less detailed way.