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Visibility in Hierarchical Systems
2009 January, 19
176 pages
Language: English
Team(s): DISTRIBCOM
Summary:
Hierarchical systems provide an elegant mechanism to analyze system functionality at different levels of abstraction. They are usually constructed in a top-down or bottom-up fashion level by level. As a result, by construction, visibility of entities in a hierarchical system is restricted to adjacent (parent-child) levels. Such restricted visibility is often not sufficient for real-life scenarios. On the other hand, allowing arbitrary interaction among the hierarchical entities, without any restrictions, is not an acceptable solution either due to security concerns. In this thesis, we address two sub-problems of the visibility issue in hierarchical systems. First, we consider the problem of defining a visibility model, given the visibility requirements and restrictions of the different entities in a hierarchy. We present graph based visibility models for two specific hierarchical systems: P2P Communities and Web services compositions. Second, we deal with the orthogonal problem of determining the visibility requirements of the given hierarchy such that a specific property holds. We give both absolute and approximate algorithms to determine the minimal visibility required by a hierarchical Web services composition to provide the property of transactional atomicity.