A contract-oriented middleware

Developing distributed applications typically requires to integrate new code with legacy third-party services, e.g., e-commerce facilities, maps, etc. These services cannot always be assumed to smoothly collaborate with each other; rather, they live in a “wild” environment where they must compete for resources, and possibly diverge from the expected behaviour if they find it convenient to do so. To overcome these issues, some recent works have proposed to discipline the interaction of mutually distrusting services through behavioural contracts. The idea is a dynamic composition, where only those services with compliant contracts can establish sessions through which they interact. Compliance between contracts guarantees that, if services behave honestly, they will enjoy safe interactions. We exploit a theory of timed behavioural contracts to formalise, design and implement a message-oriented middleware where distributed services can be dynamically composed, and their interaction monitored to detect contract violations. We show that the middleware allows to reduce the complexity of developing distributed applications, by relieving programmers from the need to explicitly deal with the misbehaviour of external services.