Many-Valued Institutions for Constraint Specification

We advance a general technique for enriching logical systems with soft constraints, making them suitable for specifying complex software systems where parts are put together not just based on how they meet certain functional requirements but also on how they optimise certain constraints. This added expressive power is required, for example, for capturing quality attributes that need to be optimised or, more generally, for formalising what are usually called service-level agreements. More specifically, we show how institutions endowed with a graded semantic consequence can accommodate soft-constraint satisfaction problems. We illustrate our approach by showing how, in the context of service discovery, one can quantify the compatibility of two specifications and thus formalise the selection of the most promising provider of a required resource.Peer Reviewe

A logical approach for behavioural composition of scenario-based models

As modern systems become more complex, design approaches model different aspects of the system separately. When considering (intra and inter) system interactions, it is usual to model individual scenarios using UML’s sequence diagrams. Given a set of scenarios we then need to check whether these are consistent and can be combined for a better understanding of the overall behaviour. This paper addresses this by presenting a novel formal technique for composing behavioural models at the metamodel level through exact metamodel restriction (EMR). In our approach a sequence diagram can be completely described by a set of logical constraints at the metamodel level. When composing sequence diagrams we take the union of the sets of logical constraints for each diagram and additional behavioural constraints that describe the matching composition glue. A formal semantics for composition in accordance with the glue guides our model transformation to Alloy. Alloy’s fully automated constraint solver gives us the solution. Our technique has been implemented as an Eclipse plugin SD2Alloy.Postprin

Automatic Quality-of-Service Evaluation in Service-Oriented Computing

Part 5: Tools (2)International audienceFormally describing and analysing quantitative requirements of software components might be important in software engineering; in the paradigm of API-based software systems might be vital. Quantitative requirements can be thought as characterising the Quality of Service – QoS provided by a service thus, useful as a way of classifying and ranking them according to specific needs. An efficient and automatic analysis of this type of requirements could provide the means for enabling dynamic establishing of Service Level Agreements – SLA, allowing for the automatisation of the Service Broker.In this paper we propose the use of a language for describing QoS contracts based on convex specification, and a two-phase analysis procedure for evaluating contract satisfaction based on the state of the art techniques used for hybrid system verification. The first phase of the procedure responds to the observation that when services are registered in repositories, their contracts are stored for subsequent use in negotiating SLAs. In such a context, a process phase of contract minimisation might lead to great efficiency gain when the second, and recurrent, phase of determining QoS compliance is run