Henschen, L.J., Park, H.S., "Compiling the GCWA," Foundation of Deductive Databases and Logic Programming , (J. Minker, Ed.), Morgan Kaufmann Publishers, Los Altos, CA, 1988, pp. 395-438.  Home/Search   Document Not in Database   Summary   Related Articles

....consesus of how to derive negative information from a database [4, 18] However, for disjunctive databases, the situation is less satisfactory. Minker s Generalized Closed World Assumption (GCWA) 15] is perhaps the 1 most widely considered semantics for disjunctive databases. For instance, see [9, 10, 28]. The GCWA reduces to Reiter s Closed World Assumption (CWA) for definite databases [28] The GCWA has been extended in various ways. Yahya and Henschen proposed Extended Generalized Closed World Assumption (EGCWA) for non unit negative clauses [28] Under the EGCWA, a negative clause C is ....

....M of DB. Clearly, M is a model of GCWA(DB) Hence DB [ GCWA(DB) 6 :A. 2 Under the GCWA, it is essential to find algorithms to determine if :A is derivable, where A is a ground atom. Some work has been done on this problem and these methods are based on finding resolutions for a set of clauses [28, 10]. This problem is likely to be intractable. We show this by proving its complement is NP hard, even when the set of clauses in a database is ground and contains no negative clauses. For a discussion on intractable problems, interested readers please refer to [6] Under the assumptions that ....

[Article contains additional citation context not shown here]

Henschen, L.J., Park, H.S., "Compiling the GCWA," Foundation of Deductive Databases and Logic Programming , (J. Minker, Ed.), Morgan Kaufmann Publishers, Los Altos, CA, 1988, pp. 395-438.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC