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作者机构:Univ Basque Country Dept Lenguajes & Sistemas Informat San Sebastian Spain
出 版 物:《ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE》 (理论计算机科学电子札记)
年 卷 期:2005年第137卷第1期
页 面:5-24页
学科分类:08[工学] 0812[工学-计算机科学与技术(可授工学、理学学位)]
基 金:TIC 2001-2476-C03 TIN2004-079250-C03-03
主 题:local variables logic programming program transformation
摘 要:In logic programming, a variable is said to be local if it occurs in a clause body but not in its head atom. It is well-known that local variables are the main cause of inefficiency (sometimes even incompleteness) in negative goal computation. The problem is twofold. First, the negation of a clause body that contains a local variables is not expressible without universal quantification, whereas the abscence of local variables guarantees that universal quantification can be avoided to compute negation. Second, computation of universal quantification is an intrinsically difficult task. In this paper, we introduce an effective method that takes a definite logic program and transforms it into a local variable free (definite) program. Source and target programs are equivalent w.r.t. three-valued logical consequences of program completion. In further work, we plan to extend our results to normal logic programs.