A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....the substitutions associated to a resolvent in any SLD refutation. The knowledge about partial answers is important for program analysis [11] to characterize the semantics of concurrent languages [16] and to characterize universal termination, which in turn is useful for the semantics of PROLOG [2, 4]. 6 ffl call patterns (denoted by pt) which are the atoms (procedure calls) selected in any SLD derivation, and correct call patterns (denoted by cpt) which are the atoms (procedure calls) selected in any SLD refutation. Call patterns make it possible to derive properties of procedure calls, ....

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.

....this framework we define a semantics for CLP that takes into account the prolog search rule, that is the left most selection rule and depth first search strategy. The semantics we present here is a reconstruction in the style of [10] of that in [9] Our first formulation ( 9] was a refinement of [2]. We chose to translate our semantics in the language of [10] because its structured approach seems to yield a more clean formulation. The paper is organized as follows. In section 2 we recall some notions from the theory of lattices and orders that will be used in the sequel. In section 3 we ....

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.

....built in s like if then 2 and if then else 3. Our results can be considered as the natural evolution of a series of previous results. The first is [8] where an attempt to model divergence is developed in a fixpoint framework. A more adequate semantics for modeling divergence is presented in [4] as an abstraction of a more concrete semantics given in terms of resultants. A resultant H : GammaB, where B is a non empty set of goals, is abstracted into a divergent atom e H, representing computation which is still in progress and which can possibly remove all the following atoms observed ....

....which can possibly remove all the following atoms observed in the computation. Note that the semantic domain consists of sequences rather than sets of atoms, in order to model the relation between atoms implied by the backtracking semantics of Prolog. A further development of the semantics in [4] can be found in [12] where the problem of the abstract semantics (useful for program analysis) is tackled, and the new feature of downward approximation of constraints is introduced; A further development of this line of research is [13] where the semantics is extended to deal with the cut ....

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint Semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, 1993.

....to the case of approximations of real Prolog, featuring some non logical primitives. The idea is to base the construction on recently proposed extensions of the S semantics which allow us to handle constructive negation [35,16,7] some Prolog primitives [1,11,28] and the Prolog computation rule [2,4]. ....

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming. The MIT Press, Cambridge, Mass., 1993.

.... 1 (617)253 1922, Fax: 1(617)253 3480, Email: miccianc theory.lcs.mit.edu Modelling control is attractive because it would allow new kinds of analyses and would improve the precision of existing ones. Several attempts to enhance traditional semantics with control related features have been made [2, 3, 5], and abstract interpretation frameworks that handle prolog search rule and cut have started to appear [6] However, none of [2, 3, 5] was shown to be actually usable for abstract interpretation, and [6] is not completely satisfactory from a theoretical point of view. In fact in [6] it is argued ....

....kinds of analyses and would improve the precision of existing ones. Several attempts to enhance traditional semantics with control related features have been made [2, 3, 5] and abstract interpretation frameworks that handle prolog search rule and cut have started to appear [6] However, none of [2, 3, 5] was shown to be actually usable for abstract interpretation, and [6] is not completely satisfactory from a theoretical point of view. In fact in [6] it is argued that there is no natural idea of collecting semantics for PROLOG, and the abstract semantics is defined by resorting to a notion of ....

[Article contains additional citation context not shown here]

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389, Cambridge, Mass., 1993. The MIT Press.

....first into a computed answer denotational semantics and the second into a call pattern denotational semantics. These two semantics admit a bottom up formulation only. All proofs not contained in this paper can be found in [22] 2 Related works There exist many formalisations for subsets of Prolog [1,3,9,24,10,11,16,17,21], and even a formalisation for full Prolog [2] We must therefore justify why a new semantics for a subset of Prolog (more precisely, Prolog with the cut but without database and set operations) is needed. A common weakness of previous approaches (except [1] and [2] when used for abstract ....

....show how the cut operator can be easily handled in this context. Our semantics can be considered as the natural evolution of a series of previous proposals. The first is [11] where divergence is modelled in a fixpoint framework. A more adequate semantics for modelling divergence is presented in [3] as an abstraction of a more concrete semantics given in terms of resultants. A resultant H : GammaB, where B is a non empty set of goals, is abstracted into a divergent atom f H, representing a computation which is still in progress and which can possibly remove all the following atoms ....

[Article contains additional citation context not shown here]

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint Semantics for Prolog. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, 1993.

....into an ask tell constraint program, with the ask constraints expressing the termination properties. ffl the oracle semantics in [4] which is parametric w.r.t. an oracle which embodies the control strategy (and the oracle can be specialized to the PROLOG case) ffl the fixpoint semantics in [6], which is simpler and closer to the s semantics and provides a direct modeling of the PROLOG control. We decided to choose the last semantics, which will be briefly recalled in Section 2, because it is definitely the most adequate to our aims, even if there are some problems, mainly related to ....

....conveyed by b A is that the corresponding derivation is partial and therefore potentially divergent. Concepts similar to the one of divergent atom have also been considered in some semantics for logic programs with the aim of modeling termination [31] and finite success [18] The first step in [6] is the definition of an extended base BE = f b A j A 2 Bg [ B, where B is the set of non ground atoms built on the program signature modulo variance. Interpretations are sets of sequences of atoms from BE . The set of interpretations (B E ) is a complete lattice. The immediate consequences ....

[Article contains additional citation context not shown here]

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.

....used in [7] to obtain a semantics compositional wrt the union of programs, here our aim was to model resultants and other observables such as call patterns and partial answers. These observables were considered also in [15] without taking into account the selection rule. Also related are the works [3, 4] which, using a more complex semantic domain, aim at a semantics modeling the Prolog deep first search strategy. More recently, the paper [9] constructs an algebraic framework which, starting from a semantics similar to our resultants semantics, allows to derive several different semantics ....

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.

....property iff there exists a frontier of a partial SLD tree for G (obtainable using a suitable abstraction of the resultant semantics and theorem 5.14) such that all the atoms in the frontier are not labeled as partial answers. This information is very important for the semantics of PROLOG [11, 17] and of all solutions metapredicates [40] ffl A goal G finitely fails iff there exist a finite number of frontiers for G, all the atoms in the frontiers of G are labeled as partial. This information is useful to get a bottom up characterization of SLDNFresolution [95] The information in ....

....with clauses of a given goal. Therefore, the semantics encodes the ordered trees of resultants for any goal. Clearly, if we are interested in some specific observable, the semantics O R (P ) contains too much information and can usefully be abstracted. One such abstraction is presented in [17]. It has been designed to capture the set of (PROLOG) computed answer substitutions (p.a.s. as observable, i.e. the set of answers which can be reached by using PROLOG s control. The observational equivalence induced by p.a.s. is the following. Definition 6.21 Let P 1 ; P 2 be pure PROLOG ....

[Article contains additional citation context not shown here]

A. Bossi, M. Bugliesi, and M. Fabris. Fixpoint semantics for PROLOG. In D. S. Warren, editor, Proc. Tenth Int'l Conf. on Logic Programming, pages 374--389. The MIT Press, Cambridge, Mass., 1993.

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