D4.1, Internal
Integration Formalism
Short Description:
The report provides the declarative definition of the internal
integration formalism. In particular, we evidence that it was already
implicit in the proposal that the internal integration formalism is
based on Disjunctive Logic Programming (DLP). Indeed, the rewriting
performed by the Query Reformulator module produces DLP programs, and
we planned to employ a DLP system for the integration. However,
thinking on possible applications, we realized that standard DLP is not
sufficient, as real life queries often require to aggregate
data'', which is not possible in standard DLP. Thus, we extended DLP by
aggregate functions in order to support some form of aggregate queries
in the language.