Optimized Querying of Integrated Data over the Web
Information Integration is the problem of providing a uniform access to multiple and heterogeneous data sources. The most common approach to this task, called global-as-view, consists in providing a global schema of the data, in which each relation is defined as a view over a set of data sources. Recent works deal with this problem in the case of limited source capabilities, where, in general, sources can only be accessed respecting certain binding patterns for their attributes. In this case, computing the answer to a user query over the global schema cannot be done by simply substituting the concepts appearing in the query with their definitions. Instead, it may require the evaluation of a suitable recursive Datalog program.