H ETS User Guide – Version 0 . 98 –

The central idea of the Heterogeneous Tool Set (HETS) is to provide an open source general framework for formal methods integration and proof management. One can think of HETS acting like a motherboard where different expansion cards can be plugged in, the expansion cards here being individual logics (with their analysis and proof tools) as well as logic translations. Individual logics and their analysis and proof tools can be plugged into the HETS motherboard using an object-oriented interface based on institutions [18]. The HETS motherboard already has plugged in a number of expansion cards (e.g., the theorem provers Isabelle, SPASS and more, as well as model finders). Hence, a variety of tools is available, without the need to hard-wire each tool to the logic at hand. HETS supports a number of input languages directly, such as CASL, Common Logic, OWL-DL, Haskell, and Maude. For heterogeneous specification, HETS offers the language heterogeneous CASL. Heterogeneous CASL (HETCASL) generalises the structuring constructs of CASL [11, 36] to arbitrary logics (if they are formalised as institutions and plugged into the HETS motherboard), as well as to heterogeneous combination of specification written in different logics. See Fig. 2 for a simple subset of the HETCASL syntax, where basic specifications are unstructured specifications or modules written in a specific logic. The graph of currently supported logics and logic translations (the latter are also called comorphisms) is shown in Fig. 3, and the degree of support by HETS in Fig. 4. With heterogeneous structured specifications, it is possible to combine and rename specifications, hide parts thereof, and also translate them to other logics. Architectural specifications prescribe the structure of implementations. Specifi-