Fresh-Variable Automata: Application to Service Composition

Abstract

To model Web services handling data from an infinite domain, or with multiple sessions, we introduce fresh-variable automata, a simple extension of finite-state automata in which some transitions are labeled with variables that can be refreshed in some specified states. We prove several closure properties for this class of automata and study their decision problems. We then introduce a notion of simulation that enables us to reduce the Web service composition problem to the construction of a simulation of a target service by the asynchronous product of existing services, and prove that this construction is computable.

Weighted Recognizability over Infinite Alphabets

“…n , q (2) n of A Gj over u, for every j ∈ J. Conversely, for every path P (Gj ) u of A Gj over u (j ∈ J) there are two paths P u (1) of A (1) (Σ (2) ,V1) over u (1) and…”

“…∪ {y}, where y denotes a new free variable different from y (1) and y (2) . We consider the wva A = Σ, A with A = (Q, in, wt, ter) where in and ter are defined, for every q ∈ Q, respectively by…”

“…u is obtained from u (2) by replacing every occurrence of y (2) with y. We define the valid relabeling h ∈ V R (Γ) which coincides with…”

“…over u (2) respectively, obtained in the obvious way. Moreover, in case weight P (Gj ) u = 0, for every j ∈ J, it holds…”

“…Despite their simplicity, variable automata and their extensions appeared to be expressive enough for several applications. Indeed, in [2] the authors introduced fresh variable automata to describe web services in which the agents exchange data ranging over infinite domains. Furthermore, in [3], fresh variable automata were equipped with guards consisting of equalities and disequalities.…”