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Acta Informatica

, Volume 25, Issue 2, pp 111–153 | Cite as

Crypt-equivalent algebraic specifications

  • F. L. Bauer
  • M. Wirsing
Article

Summary

Equivalence is a fundamental notion for the semantic analysis of algebraic specifications. In this paper the notion of “crypt-equivalence” is introduced and studied w.r.t. two “loose” approaches to the semantics of an algebraic specification T: the class of all first-order models of T and the class of all term-generated models of T. Two specifications are called crypt-equivalent if for one specification there exists a predicate logic formula which implicitly defines an expansion (by new functions) of every model of that specification in such a way that the expansion (after forgetting unnecessary functions) is homologous to a model of the other specification, and if vice versa there exists another predicate logic formula with the same properties for the other specification. We speak of “first-order crypt-equivalence” if this holds for all first-order models, and of “inductive crypt-equivalence” if this holds for all term-generated models. Characterizations and structural properties of these notions are studied. In particular, it is shown that first order crypt-equivalence is equivalent to the existence of explicit definitions and that in case of “positive definability” two first-order crypt-equivalent specifications admit the same categories of models and homomorphisms. Similarly, two specifications which are inductively crypt-equivalent via sufficiently complete implicit definitions determine the same associated categories. Moreover, crypt-equivalence is compared with other notions of equivalence for algebraic specifications: in particular, it is shown that first-order cryptequivalence is strictly coarser than “abstract semantic equivalence” and that inductive crypt-equivalence is strictly finer than “inductive simulation equivalence” and “implementation equivalence”.

Keywords

Operating System Data Structure Communication Network Information Theory Structural Property 
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.

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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • F. L. Bauer
    • 1
  • M. Wirsing
    • 2
  1. 1.Institut für InformatikTechnische Universität MünchenMünchen 2Germany
  2. 2.Fakultät für Mathematik und InformatikUniversität PassauPassauGermany

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