Structured operational semantics as a specification language

  • Authors:

  • Bard Bloom

  • Affiliations:

  • Cornell University, Ithaca, NY

  • Venue:
  • POPL '95 Proceedings of the 22nd ACM SIGPLAN-SIGACT symposium on Principles of programming languages
  • Year:
  • 1995

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Abstract

Standard specification languages have very limited abilities to define new operations on processes. We introduce the concept of a Protean specification language, with general definitional facilities supported by the appropriate theory. Protean languages allow elegant, readable, and useful specifications at all levels of abstraction. A good Protean specification language will admit methods of verifying that one specification is a refinement of another. We sketch a family of Protean specification languages (with references to the full details) which allow a vast amount of expressive power in defining operations, but nonetheless have all the essential theoretical and specification power of CCS and ACP.We illustrate these techniques by presenting several specifications of the job of protecting an arbitrary server by a checkpoint/backup scheme. The high-level specification of the protected server simply says, “It does everything it did before, and it doesn't crash.” The middle-level specification describes checkpointing cleanly and abstractly, without prescribing any particular implementation. The low-level specification is fairly close to an implementation. We show the high- and medium-level specifications equivalent by bisimulation relation techniques, and the medium- and low-level specifications equivalent by equational reasoning using automatically-generated equations. We also show that the operations expressing checkpointing behavior are not definable in standard process algebras.