Spheres of visibility[Web services]

The most promising feature of the Web services platform is its ability to form new services by combining the capabilities of existing services, i.e., its compos ability. The existing services may themselves be composed of other services, leading to a hierarchical composition. In a hierarchical composition, providers vary in the visibility they have over the other providers in the composition. For example, a provider may not be aware of any providers in the hierarchy other than its parent and children. On the other hand, a provider may be aware of all other providers in the hierarchy. Towards this end, we introduce the notion of spheres of visibility (SoV) as an abstraction to capture the upward/downward visibility aspects of the providers in a hierarchical composition. The latter part of this paper deals with compensation. We outline a compensation mechanism for hierarchical compositions conforming to the visibility restrictions modeled as SoV.