Can One Escape Red Chains? Regular Path Queries Determinacy is Undecidable

Abstract

For a given set of queries (which are expressions in some query language) Q = {Q 1 , Q 2 , . . . Q k } and for another query Q 0 we say that Q determines Q 0 if -informally speaking -for every database D, the information contained in the viewsQuery Determinacy Problem is the problem of deciding, for given Q and Q 0 , whether Q determines Q 0 . Many versions of this problem, for different query languages, were studied in database theory. In this paper we solve a problem stated in [CGLV02] and show that Query Determinacy Problem is undecidable for the Regular Path Queries -the paradigmatic query language of graph databases.