On Syntactic and Semantic Dependencies in Service-Oriented Architectures

In service oriented architectures, components provide services on their output ports and consume services from other components on their input ports. Thereby, a component is said to depend on another component if the former consumes a service provided by the latter. This notion of dependency (which we call syntactic dependency) is used by many architecture analysis tools as a measure for system maintainability. With this paper, we introduce a weaker notion of dependency, still sufficient, however, to guarantee semantic independence between components. Thereby, we discover the concepts of weak and strong semantic dependency and prove that strong semantic dependency indeed implies syntactic dependency. Our alternative notion of dependency paves the way to more precise dependency analysis tools. Moreover, our results about the different types of dependencies can be used for the verification of semantic independence.