Advertisement

NAPAW 92 pp 216-230 | Cite as

A π-calculus Semantics of Logical Variables and Unification

  • Brian J. Ross
Conference paper
Part of the Workshops in Computing book series (WORKSHOPS COMP.)

Abstract

A π-calculus semantics of terms and logical variables, environment creation visavis term copying and variable refreshing, and sequential unification is presented. The π-calculus’s object-oriented approach to modelling evolving communication structures is used to model the evolving communication environment found in concurrent logic program computations. The novelty of this semantics is that it explicitly models logic variables as active channels. These channels are referenced by π-calculus channel labels, and when used in concert with the v restriction operator, model variable scopes and environments. Sequential unification without occurs check is modelled by traversing term expressions, and binding variables to terms as appropriate. The π-calculus is well-suited for this, as its object-oriented view of concurrency permits the modelling of the object passing and variable redirection that occurs during unification. This semantics is a central component of a more comprehensive operational semantics of concurrent logic programming languages currently being developed.

Keywords

Logic Program Term Structure Operational Semantic Process Algebra Variable Channel 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [Bec87]
    L. Beckman. Towards an Operational Semantics for Concurrent Logic Programming Languages. PhD thesis, Uppsala University, 1987.Google Scholar
  2. BH92] M. Belmesk and Z. Habbas. A Process Calculus with Shared Variables. Journal of Computers and Artificial Intelligence,1992. (to appear).Google Scholar
  3. [CM81]
    W.F. Clocksin and C.S. Mellish. Programming in Prolog. Springer- Verlag, 1981.Google Scholar
  4. dBP92] F.S. de Boer and C. Palamidessi. A process algebra of concurrent constraint programming. In Joint International Conference and Symposium on Logic Programming,Washington, D.C., 1992. MIT Press.Google Scholar
  5. [Lin84]
    G. Lindstrom. OR-parallelism on applicative architectures. In 2 nd International Logic Programming Conference, Uppsala, 1984.Google Scholar
  6. [L1o84]
    J.W. Lloyd. Foundations of Logic Programming. Springer-Verlag, 1984.Google Scholar
  7. [Mi189]
    R. Milner. Communication and Concurrency. Prentice Hall, 1989.Google Scholar
  8. [Mi191]
    R. Milner. The Polyadic ir-Calculus: A Tutorial. Technical Report ECS-LFCS-91–180, LFCS, U. of Edinburgh, 1991.Google Scholar
  9. [MPW89a]
    R. Milner, J. Parrow, and D. Walker. A Calculus of Mobile Processes, Part I. Technical Report ECS-LFCS-89–85, LFCS, U. of Edinburgh, 1989.Google Scholar
  10. [MPW89b]
    R. Milner, J. Parrow, and D. Walker. A Calculus of Mobile Processes, Part IL Technical Report ECS-LFCS-89–86, LFCS, U. of Edinburgh, 1989.Google Scholar
  11. Ros92a] B.J. Ross. A a—calculus Semantics of Committed Logic Program Control, 1992. In preparation.Google Scholar
  12. [Ros92b]
    B.J. Ross. An Algebraic Semantics of Prolog Control. PhD thesis, University of Edinburgh, Scotland, 1992.Google Scholar
  13. [Sha87]
    E.Y. Shapiro. Concurrent Prolog vol. 1 and 2. MIT Press, 1987.Google Scholar
  14. [SR90]
    V. Saraswat and M. Rinard. Concurrent Constraint Programming. In POPL, pages 232–245, San Francisco, 1990.Google Scholar
  15. [Ued86]
    K. Ueda. Guarded Horn Clauses. PhD thesis, University of Tokyo, 1986.Google Scholar
  16. [Wa190]
    D. Walker. ir-calculus Semantics of Object-Oriented Programming Languages. Technical Report ECS-LFCS-90–122, LFCS, U. of Edinburgh, 1990.Google Scholar

Copyright information

© British Computer Society 1993

Authors and Affiliations

  • Brian J. Ross
    • 1
  1. 1.Department of Computer ScienceBrock UniversitySt. CatharinesCanada

Personalised recommendations