A theory of retractable and speculative contracts

Franco Barbanera (1) , Ivan Lanese (2) , Ugo De'Liguoro (3)

1 Unict - Università degli studi di Catania = University of Catania
2 FOCUS - Foundations of Component-based Ubiquitous Systems
3 Dipartimento di Informatica [Torino]

Behavioral contracts are abstract descriptions of expected communication patterns followed by either clients or servers during their interaction. Behavioral contracts come naturally equipped with a notion of compliance: when a client and a server follow compliant contracts, their interaction is guaranteed to progress or successfully complete. We study two extensions of behavioral contracts, retractable contracts dealing with backtracking and speculative contracts dealing with speculative execution. We show that the two extensions give rise to the same notion of compliance. As a consequence, they also give rise to the same subcontract relation, which determines when one server can be replaced by another preserving compliance. Moreover, compliance and subcontract relation are both decidable in quadratic time. Finally, we study the relationship between retractable contracts and calculi for reversible computing.

Keywords: Behavioral contracts; backtracking; speculative execution; compliance; reversible computing

Domains: Programming Languages [cs.PL]; Formal Languages and Automata Theory [cs.FL]

Franco Barbanera, Ivan Lanese, Ugo De'Liguoro. A theory of retractable and speculative contracts. Science of Computer Programming, 2018, 167, pp.25 - 50. ⟨10.1016/j.scico.2018.06.005⟩. ⟨hal-01912858⟩