Semiring-based constraint satisfaction and optimization

Abstract

We introduce a general framework for constraint satisfaction and optimization where classical CSPs, fuzzy CSPs, weighted CSPs, partial constraint satisfaction, and others can be easily cast. The framework is based on a semiring structure, where the set of the semiring specifies the values to be associated with each tuple of values of the variable domain, and the two semiring operations (+ and X) model constraint projection and combination respectively. Local consistency algorithms, as usually used for classical CSPs, can be exploited in this general framework as well, provided that certain conditions on the semiring operations are satisfied. We then show how this framework can be used to model both old and new constraint solving and optimization. schemes, thus allowing one to both formally justify many informally taken choices in existing schemes, and to prove that local consistency techniques can be used also in newly defined schemes

Coordination Via Types in an Event-Based Framework

“…A lambda reaction + x : τ c λτ → B .B installs a "generic reaction" for the topic τ in the component interface; this reaction handles all signals with topic τ, regardless of their session. In the reaction behavior B, τ and x are bound by the lambda reaction 1 .…”

“…The signals sent to C 1 and C 2 are both related to the same session τ that is later used by J to apply the synchronization on the same workflow. Clearly, the two intermediate services C 1 and C 2 can concurrently perform their tasks, while the execution of the service J can be triggered only after the completion of their execution.…”

Semantic-Based Development of Service-Oriented Systems

“…Instead of determining just a subset of admissible domain elements, a soft constraint assigns a grade-to be chosen from a set of finite or infinitely many "preference" values-to each element of the application domain. Bistarelli, Montanari and Rossi [6,5] have developed a very elegant semiring based theory of soft constraints where many different kinds of soft constraints can be represented and combined in a uniform way over so-called constraint semirings In SENSORIA we are developing a language which extends the c-semiring approach with possibilities to specify preferences between constraints and to vary the constraints according to a context. This simplifies the description of behaviours of systems in a dynamically changing environment and with complex trade-offs between conflicting properties.…”

Reasoning about Secure Interoperation Using Soft Constraints

“…Sometimes, when a deeper analysis of a problem is required, soft constraints are used instead [Bistarelli et al, 1997, Bistarelli, 2004. Soft constraints associate a qualitative or quantitative value either to the entire constraint or to each assignment of its variables.…”

“…In this paper we describe how constraints [Bistarelli et al, 1997, Bistarelli, 2004, Wallace, 1996 provide a practical and natural approach to modelling and solving the secure interoperation problem. Constraint solving is an emerging software technology for declarative description and effective solving of large problems.…”