Title
View determinacy for preserving selected information in data transformationsView determinacy for preserving selected information in data transformations
Author
Faculty/Department
Faculty of Sciences. Mathematics and Computer Science
Research group
Advanced Database Research and Modeling (ADReM)
Publication type
article
Publication
London,
Subject
Computer. Automation
Source (journal)
Information systems. - London
Volume/pages
37(2012):1, p. 1-12
ISSN
0306-4379
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Abstract
When transforming data one often wants certain information in the data source to be preserved, i.e.,we identify parts of the source data and require these parts to be transformed without loss of information. We characterize the preservation of selected information in terms of the notions of invertibility and query preservation, in a setting when transformations are specified as a view V (a set of queries), and source information is selected by a query Q. We investigate the problem for determining whether transformations V preserve the information selected by Q. (1) We show that the notion of invertibility coincides with view determinacy studied for query rewriting. (2) We establish the undecidability of the problem when either Q or V is in DATALOG or first-order logic, for invertibility and query preservation. (3) When Q and V are conjunctive queries (CQ), the problem is as hard as view determinacy for CQ queries and CQ views, an open problem. Nevertheless, we provide complexity bounds of the problem, either in ptime or np-complete, when V ranges over subclasses of CQ (i.e.,SP, SC, PC), and when Q is assumed to be a minimal CQ query or not. (4) We show that CQ is complete for L-to-CQ rewriting when L is SP, SC or PC, i.e.,every CQ query can be rewritten in terms of SP, SC or PC views using a query in CQ.
E-info
https://repository.uantwerpen.be/docman/iruaauth/7ffcec/f5125fad956.pdf