Specifying variability in service contracts

In Service Oriented Computing (SOC) contracts characterise the behavioural conformance of a composition of services and guarantee that the composition does not lead to spurious results. Variability features can enable services to adapt to customer requirements and to changes in the context in which they execute. We extend a recently introduced formal model of service contracts to specify variability mechanisms in a composition of services. Necessary and permitted service requests can be defined and triggered to increase adaptability. The compositional rules of the original formalism are enriched to fulfil all necessary requirements and the maximal number of permitted ones.