Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

January 2008


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-08-37


We study conjunctive queries with unequalities (xy) and we identify cases when query containment can still be characterized by the existence of homomorphisms. We also identify a class of GLAV-like database schema mappings with unequalities, for which the chase theorem holds, and thus data exchange has the same complexity as for GLAV mappings. Finally, we define a notion of consistency and provide an algorithm to check whether a set of mappings is consistent.



Date Posted: 22 June 2009