Abstract. We present the meta-theory behind the code generation facilities of Isabelle/HOL. To bridge the gap between the source (higherorder logic with type classes) and the many possible targets (functional programming languages), we introduce an intermediate language, MiniHaskell. To relate the source and the intermediate language, both are given a semantics in terms of higher-order rewrite systems (HRSs). In a second step, type classes are removed from Mini-Haskell programs by means of a dictionary translation; we prove the correctness of this step. Building on equational logic also directly supports a simple but powerful algorithm and data refinement concept.

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Regression testing is an important software maintenance activity to ensure the integrity of a software after modification. However, most methods and tools developed for software testing today do not work well for database applications; these tools only work well if applications are stateless or tests can be designed in such a way that they do not alter the state. To execute tests for database applications efficiently, the challenge is to control the state of the database during testing and to order the test runs such that expensive database reset operations that bring the database into the right state need to be executed as seldom as possible. This work devises a regression testing framework for database applications so that test runs can be executed in parallel. The goal is to achieve linear speed-up and/or exploit the available resources as well as possible. This problem is challenging because parallel testing needs to consider both load balancing and controlling the state of the database. Experimental results show that test run execution can achieve linear speed-up by using the proposed framework.

Abstract. The paper shows how the code generator of Isabelle/HOL supports data refinement, i.e., providing efficient code for operations on abstract types, e.g., sets or numbers. This allows all tools that employ code generation, e.g., Quickcheck or proof by evaluation, to compute with these abstract types. At the core is an extension of the code generator to deal with data type invariants. In order to automate the process of setting up specific data refinements, two packages for transferring definitions and theorems between types are exploited.

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