Refine and gabriel: support for refinement and tactics

Using Morgan's refinement calculus, we can write software in a precise and consistent way. Nevertheless, this may involve long and repetitive developments. Several refinement strategies are useful in different developments, and even in different points of a single development. A lot is gained by identifying these strategies, documenting them as tactics, and using them as single transformation rules. With this motivation, we have designed ArcAngel, a tactic language especially tailored for refinement; we have formalised its semantics and studied its algebraic laws. Even with the use of tactics, however refinement can be a hard task and the use of tools is essential in practice. In this paper we present Refine and Gabriel, interactive, user-friendly tools that allow us to use the refinement calculus with the support of ArcAngel tactics.