M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

No context found.

M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995.

.... recall: i) the strategies for deriving tail recursive programs [3,17] ii) the promotion strategy for reducing nondeterminism within generate and test programs [72] iii) the strategy for eliminating unnecessary variables and thus, avoiding multiple traversals and intermediate data structures [58], and (iv) the strategy for reducing nondeterminism during program specialization [56] The general unfold fold transformation strategy we have presented in Section 2.3, extends the above mentioned strategies to the case of programs with locally strati ed negation. The interesting fact to notice ....

....order speci cations, and (3) program veri cation. The main advantage of developing several techniques for program derivation in a uni ed framework, is that we may reuse similar techniques in di erent contexts. For instance, the program transformation strategy for eliminating unnecessary variables [58] may be reused as a quanti er elimination technique for theorem proving [55] Moreover, our uni ed view of program derivation allows us to design a general tool which may be used for machine assisted program transformation, synthesis, and veri cation. It should be pointed out that, besides the ....

M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995.

....into proof strategies. In particular, at Step 2 of our proof method, in order to direct the transformation rules, we may use the so called UFS strategy which is an enhancement of a strategy introduced in the case of de nite logic programs for deriving programs without existential variables [21]. When our UFS strategy terminates, it derives from P F (f; either (i) a new program of the form Q f , in which case M(P ) j= or (ii) a program where no clause has head predicate f , in which case M(P ) 6j= We will show that the UFS strategy indeed terminates for some classes of ....

.... a strategy for guiding the application of the transformation rules, and indeed, in this section we present such a strategy, called UFS (short for Unfold Fold proof Strategy) It is an extension of the strategy introduced in the case of de nite logic programs for eliminating existential variables [21]. The basic idea is that by eliminating existential variables, from P F (f; we may derive a program, say S, such that Def (f ; S ) is a propositional program. Then, we can transform S by using the clause deletion, unfolding, tautology, and goal replacement rules, into a program T ....

M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995.

....various transformation methods have been proposed, such as nite di erencing [112] composition or deforestation [66, 150] and tupling [116] See also [67, 113, 118] for surveys. For logic programs two main methods have been considered: loop fusion [52] and elimination of unnecessary variables [125]. The aim of loop fusion is to transform a program which computes a predicate de ned by the composition of two independent recursive predicates, into a program where the computations corresponding to these two predicates are performed by one predicate only. Using loop fusion one may avoid the ....

....recursive predicates, into a program where the computations corresponding to these two predicates are performed by one predicate only. Using loop fusion one may avoid the multiple traversal of data structures and the construction of intermediate data structures. The method presented in [125] may be used for deriving programs without unnecessary variables. A variable X of a clause C is said to be unnecessary if at least one of the following two conditions holds: 1) X occurs more than once in the body of C (in this case we say that X is a shared variable) 2) X does not occur in the ....

[Article contains additional citation context not shown here]

M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995. 85

....into proof strategies. In particular, at Step 2 of our proof method, in order to direct the transformation rules, we may use the so called UFS strategy which is an enhancement of a strategy introduced in the case of de nite logic programs for deriving programs without existential variables [22]. When our UFS strategy terminates, it derives from P F (f; either (i) a new program of the form Q f , in which case M(P ) j= or (ii) a program where no clause has head predicate f , in which case M(P ) 6j= We will show that the UFS strategy indeed terminates for some classes of ....

.... guiding the application of the transformation rules, and indeed, in this section we present such a strategy, called UFS (short for Unfold Fold proof Strategy) The UFS strategy is an extension of the strategy introduced in the case of de nite logic programs for eliminating existential variables [22]. The basic idea is that by eliminating existential variables, from P F (f; we may derive a program, say S, such that Def (f ; S ) is a propositional program. Then, we can transform S by using the clause deletion, unfolding, tautology, and goal replacement rules, into a program T ....

M. Proietti and A. Pettorossi. Unfolding-denition-folding, in this order, for avoiding unnecessary variables in logic programs. Theoretical Computer Science, 142(1):89124, 1995.

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