Alloy is a declarative language for lightweight modelling and analysis of software. The core of the language is based on first-order relational logic, which offers an attractive balance between analysability and expressiveness. The logic is expressive enough to capture the intricacies of real systems, but is also simple enough to support fully automated analysis with the Alloy Analyzer. The Analyzer is built on a SAT-based constraint solver and provides automated simulation, checking and debugging of Alloy specifications. Because of its automated analysis and expressive logic, Alloy has been applied in a wide variety of domains. These applications have motivated a number of extensions both to the Alloy language and to its SAT-based analysis. This paper provides an overview of Alloy in the context of its three largest application domains, lightweight modelling, bounded code verification and test-case generation, and three recent application-driven extensions, an imperative extension to the language, a compiler to executable code and a proof-capable analyser based on SMT.

An approach is described for checking the methods of a class against a full specification. It shares with traditional model checking the idea of exhausting the entire space of executions within some finite bounds, and with traditional verification the idea of modular analysis, in which a method is analyzed, in isolation, for all possible calling contexts.The analysis involves an automatic two-phase reduction: first, to an intermediate form in relational logic (using a new encoding described here), and second, to a boolean formula (using existing techniques), which is then handed to an off the shelf SAT solver.A variety of implementations of the Java Collections Framework's List interface were checked against existing JML specifications. The analysis revealed bugs in the implementations, as well as errors in the specifications themselves.

Two operations commute if executing them serially in either order results in the same change of state. In a system in which commands may be issued simultaneously by different users, lack of commutativity can result in unpredictable behaviour, even if the commands are serialized, because one user's command may be preempted by another's, and thus executed in an unanticipated state. This paper describes an automated approach to analyzing commutativity. The operations are expressed as constraints in a declarative modelling language such as Alloy, and a constraint solver is used to find violating scenarios. A case study application to the beam scheduling component of a proton therapy machine (originally specified in OCL) revealed several violations of commutativity in which requests from medical technicians in treatment rooms could conflict with the actions of a beam operator in a master control room. Some of the issues involved in automating the analysis for OCL itself are also discussed.