Mutually Testing Processes

Abstract

Abstract. In the standard testing theory of DeNicola-Hennessy one process is considered to be a refinement of another if every test guaranteed by the former is also guaranteed by the latter. In the domain of web services this has been recast, with processes viewed as servers and tests as clients. In this way the standard refinement preorder between servers is determined by their ability to satisfy clients.But in this setting there is also a natural refinement preorder between clients, determined by their ability to be satisfied by servers. In more general settings where there is no distinction between clients and servers, but all processes are peers, there is a further refinement preorder based on the mutual satisfaction of peers.We give a uniform account of these three preorders. In particular we give two characterisations. The first is behavioural, in terms of traces and ready sets. The second, for finite processes, is equational.

Choreographies and Behavioural Contracts on the Way to Dynamic Updates

“…The operational semantics for the new Choreography Calculus with updates is defined in [3] only for a proper subset of well defined choreographies. 1 For instance, conditions are added in order to guarantee that every update X {r : H} injects a choreography H that considers only roles explicitly indicated in the type T of the updated part X : T [H ′ ]. Moreover, also syntactic restrictions are imposed in order to guarantee that it will never occur that two distinct scopes with the same name are contemporaneously active.…”

“…In this context, extending our contract refinement theory to updatable choreographies/orchestrations (thus getting updatable behavioural contracts) would make it possible to define a notion of semantic subtyping. We also plan to work on the complete characterization of compliance testing: work in this direction has been done in [1] where however testing is characterized only for controllable processes (i.e. processes for which there exists a compliant test) and fairness is not considered (a testing notion similar to our compliance testing is considered, where both the test and the system under test must succeed, but in the flavour of traditional testing of [17] without assuming fairness).…”

Full-Abstraction for Must Testing Preorders

“…The standard testing theory of De Nicola-Hennessy [12,15] has recently been employed to provide theoretical foundations for web-services [9,25] (where processes denote servers). To better fit that setting, in [6] this theory has been enriched with preorders for clients (tests) and peers (where both interacting parties mutually satisfy one another). Client preorders also tie testing theory with session type theory, as is outlined in [2]: they are instrumental in defining semantic models of the Gay & Hole subtyping [14] for first-order session types [3,Theorem 6.3.4] and [5,Theorem 5.2].…”

“…To solve this problem, contextual preorders usually come equipped with behavioural characterisations that avoid universal context quantification thereby facilitating reasoning. In [6] the authors develop such characterisations for the client and the peer must preorders; these preorders are however not fully-abstract, for they are defined modulo usable clients, i.e., clients that are satisfied by some server.…”

“…Usability is a pivotal notion that appears frequently in the literature of process calculi and web-service foundations, cf. viability in [18,26] and controllability in [8,24], and has already been studied, albeit for restricted or different settings, in [18,25,7,6,26]. In general though, the characterisation of usability is problematic, for solving it requires finding the conditions under which one can either (a) construct a server p that satisfies a given client, or (b) show that every p does not satisfy a given client.…”