Verifiable abstractions for contract-oriented systems

- We present a specification language for distributed systems where the interaction between agents is regulated by contracts.
- We consider the honesty property, which characterises those agents which always respect their contracts.
- We propose a sound verification technique for honesty, based on semantic abstraction and model checking.
- We describe a Maude implementation of our verification technique.
- We provide detailed proofs of all our statements, and a suite of experiments to validate our technique.

We address the problem of modelling and verifying contract-oriented systems, wherein distributed agents may advertise and stipulate contracts, but - differently from most other approaches to distributed agents - are not assumed to always respect them. A key issue is that the honesty property, which characterises those agents which respect their contracts in all possible execution contexts, is undecidable in general. The main contribution of this paper is a sound verification technique for honesty, targeted at agents modelled in a value-passing version of the calculus CO2. To do that, we safely over-approximate the honesty property by abstracting from the actual values and from the contexts a process may be engaged with. Then, we develop a model-checking technique for this abstraction, we describe its implementation in Maude, and we discuss some experiments with it.