Christian Maeder

The heterogeneous tool set, HETS

Heterogeneous specification becomes more and more important because complex systems are often specified using multiple viewpoints, involving multiple formalisms (see Fig. 1). Moreover, a formal software development process may lead to a change of formalism during the development.

Checking Conservativity with Hets

Conservative extension is an important notion in the theory of formal specification [8]. If we can implement a specification SP, we can implement any conservative extension of SP as well. Hence, a specification can be shown consistent by starting with a consistent specification and extending it using a number of conservative extension steps. This is important, because during a formal development, it is desirable to guarantee consistency of specifications as soon as possible. Checks for conservative extensions also arise in calculi for proofs in structured specifications [12,9]. Furthermore, consistency is a special case of conservativity: it is just conservativity over the empty specification. Moreover, using consistency, also non-consequence can be checked: an axiom does not follow from a specification if the specification augmented by the negation of the axiom is consistent. Finally, [3] puts forward the idea of simplifying the task of checking consistency of large theories by decomposing them with the help of an architectural specification [2]. In order to show that an architectural specification is consistent, it is necessary to show that a number of extensions are conservative (more precisely, the specifications of its generic units need to be conservative extensions of their argument specifications, and those of the non-generic units need to be consistent).

Integrating maude into hets

Maude modules can be understood as models that can be formally analyzed and verified with respect to different properties expressing various formal requirements. However, Maude lacks the formal tools to perform some of these analyses and thus they can only be done by hand. The Heterogeneous Tool Set Hets is an institution-based combination of different logics and corresponding rewriting, model checking and proof tools. We present in this paper an integration of Maude into Hets that allows to use the logics and tools already integrated in Hets with Maude specifications. To achieve such integration we have defined an institution for Maude based on preordered algebras and a comorphism between Maude and CASL, the central logic in HETS.

The VSE Refinement Method in Hets

We present the integration of refinement method of VSE verification tool, successfully used in industrial applications, in the Heterogeneous Tool Set Hets . The connection is done via introducing the dynamic logic underlying VSE and two logic translations in the logic graph of Hets . Thus the logic-independent layers of Hets are not modified and its proof management formalism can be applied to VSE specifications.