Soft Constraints for Quality Aspects in Service Oriented Architectures

We propose the use of Soft Constraints as a natural way to model Service Oriented Architecture. In the framework, constraints are used to model components and connectors and constraint aggregation is used to represent their interactions. Moreover, a specific constraint projection operator is used to highlight the service interface. The quality of a service is measured and considered when performing queries to service providers. In particular, we are here interested to aspect of dependability, that is to the trustworthiness of a computing system on the service it delivers. In our framework, the dependability score is represented by the softness level of the constraint and the measure of complex (web) services is computed by combining the levels of the components. The framework takes also in account the interaction of software agents representing distributed services, by using a constraint based concurrent language able to also decide the collaboration taking care of the required dependability score.