An algebra for commitment protocols

Abstract

Protocols enable unambiguous, smooth interactions among agents. Commitments among agents are a powerful means of developing protocols. Commitments enable flexible execution of protocols and help agents reason about protocols and plan their actions accordingly, while at the same time providing a basis for compliance checking. Multiagent systems based on commitments can conveniently and effectively model business interactions because the autonomy and heterogeneity of agents mirrors real-world businesses. Such modeling, however, requires multiagent systems to host a rich variety of protocols that can capture the needs of different applications. We show how a commitment-based semantics provides a basis for refining and aggregating protocols. We propose an approach for designing commitment protocols wherein traditional software engineering notions such as refinement and aggregation are extended to apply to protocols. We present an algebra of protocols that can be used to compose protocols by refining and merging existing ones, and does this at a level of abstraction high enough to be useful for real-world applications.

Correctness Properties for Multiagent Systems

“…Our commitment-based semantics yields a rigorous basis for protocol refinement and aggregation [19]. In principle, these properties enable reusing protocols from a repository.…”

“…We would never explicitly enumerate the potentially infinite number of possible runs, but we can use the abstract definition to show important algebraic relationships. Mallya & Singh [19] show important progress, but their approach is far from complete. Specifically, it deals with sets of runs, but does not apply directly on protocol specifications as one would find in a repository.…”

Producing Compliant Interactions: Conformance, Coverage, and Interoperability

“…Our definitions of conformance and coverage rely on the notion of run subsumption [6]. In the following, we briefly discuss run subsumption, then we formally define conformance and coverage.…”

“…That is, s ≺ τ s means that s occurs before s in τ . Run subsumption is reflexive, transitive, and antisymmetric up to state similarity [6]. Longer runs subsume shorter runs, provided they have similar states in the same temporal order.…”

Interoperation in Protocol Enactment

“…Whereas agent compliance can only be checked by monitoring the messages an agent exchanges with its peers at runtime, conformance can be verified from the agent's design. An agent's design is conformant with a protocol if it respects the semantics of the protocol; a useful semantics is obtained when considering the satisfaction of commitments [12]. The distinction between conformance and compliance is important: an agent's design may conform, but its behavior may not comply.…”