Requirement enforcement by transformation automata

The goal of this work is to treat safety and security policies as requirements to be composed in an aspectual style with a developing application. Policies can be expressed either logically or by means of automata. We introduce the concept of transformation automaton, which is an automaton whose transitions are labeled with program transformations. A transformation automaton is applied to a target program by a sound static analysis procedure. The effect is to perform a global transformation that enforces the specified policy. The semantic effect of this global transformation is explored. In previous work we discussed how the intent of an AspectJ-style aspect can be expressed precisely and abstractly as a state invariant. Here, this result is generalized to handle invariants that are conditional and stated over both events and state properties. A policy stated in such a logical format can be translated to a transformation automaton that enforces it in a target program. The translation process is defined by a collection of inference schemes that can be mechanically instantiated and then solved, at least partially automatically, by deductive calculations.