LIQUID: Logic-based Integration and Querying of Unindexed Internet Data

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The Deep Web is constituted by data that are stored outside web pages, normallyin databases or files, and are accessible by querying them through web forms.Deep Web data sources, apart from having local integrity constraints enforcedon them, are characterised by so-called access limitations, due to the inputrequirements of the forms, and such limitations restrict the set of that thatcan be ``reached'' by queries. Moreover, in general, recursive query plans areneeded to provide the maximum information as answer to a query. In the projectLIQUID (Logic-based Integration of Unindexed Internet Data), we address theproblem of integrating Deep Web sources and making them queryable through aglobal schema, representing all underlying data. The global schema employsconstraints to model properties of the domain of interest, which are notnecessarily reflected by the data stored at the heterogeneous sources. In thisproject we plan to study formalisms to represent Deep Web integration systems,and to devise scalable query processing techniques for such systems. We planto study static and dynamic techniques to reduce the query processing cost, byemploying logic-based reasoning techniques on constraints and accesslimitations. We plan to build a prototype implementing our findings. LIQUIDwill face ambitious challenges, due to the variety of formalisms and problemsinto play.