ABSTRACT

This paper improves top-down execution models of logic  programs based on 
a two-phase abstract interpretation which consists of a bottom-up analysis 
followed by a top-down one. The two-phase analysis provides an approximation 
of all (possibly non-ground) success patterns of clauses {\em relevant} to 
a query. It is specialized by considering Sato and Tamaki's depth $k$ 
abstraction as abstract function.  
By the ability of the analysis to approximate possibly non-ground success 
patterns of clauses relevant to a query, it can be statically determined 
whether some subgoals will fail during execution and some succeeding subgoals 
do not participate in success patterns of program clauses relevant to 
a given query.  
These properties are utilized to improve execution models. 
This approach can be easily applied to any top-down (parallel)
execution models.