Logical queries over views

James Bailey, Guozhu Dong, Anthony WIDJAJA To
2010 ACM Transactions on Computational Logic  
We study the problem of deciding the satisfiability of first-order logic queries over views, with our aim to delimit the boundary between the decidable and the undecidable fragments of this language. Views currently occupy a central place in database research due to their role in applications such as information integration and data warehousing. Our main result is the identification of a decidable class of first-order queries over unary conjunctive views that general the decidability of the
more » ... sical class of first-order sentences over unary relations known as the Löwenheim class. We then demonstrate how various extensions of this class lead to undecidability and also provide some expressivity results. Besides its theoretical interest, our new decidable class is potentially interesting for use in applications such as deciding implication of complex dependencies, analysis of a restricted class of active database rules, and ontology reasoning. )). A first-order view query is a first-order formula expressed solely in terms of the given views. For example, q 1 = ∃x 1 , y 1 ((V 1 (x 1 , y 1 ) ∨ V 1 ( y 1 , x 1 )) ∧ ¬V 2 (x 1 )) ∧ ∀z 1 (V 2 (z 1 ) ⇒ V 1 (z 1 , z 1 )) is an example first-order view query, but q 2 = ∃x 1 , y 1 (V 1 (x 1 , y 1 ) ∨ R( y 1 , x 1 )) is not. By expanding the view definitions, every first-order view query can clearly be rewritten to eliminate the views. Hence, first-order view queries can be thought of as a fragment of first-order logic, with
doi:10.1145/1656242.1656243 fatcat:vv2spm7q6fgmdegb7kdbwwn3ve