Service Oriented Architectures (SOAs) are constantly gaining ground for the provision of business to business as well as user-centric services, mainly in the form of Web Services technology. SOAs enable service providers to design and deploy new,composite service offerings out of existing component services. In order to match end-user expectations with respect to personalization and ease of use, these services should be designed in a manner that allows them to exhibit a certain level of context-awareness which is a basic element towards a richer end-user experience. However, in the majority of such services, context-handling is still tightly coupled with the core functionality of the service, resulting in a design which is difficult to implement and maintain. The paper proposes the decoupling of core service logic from context-related functionality by adopting a Model-driven approach based on a modified version of the ContextUML metamodel. Core service logic and context handling are treated as separate concerns at the modeling level as well as in the resulting source code where Aspect Oriented Programming (AOP) encapsulates contextdependent behavior in discrete code modules. The design of a restaurant finder service is used to portray the modified ContextUML metamodel and the service modeling process which is covered in full. Respective code snippets belonging to the executable version of the service (part of work in progress) are also provided, illustrating the transition from model to code and the resulting separation of concerns.

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In this work we study the effectiveness of mechanisms for decentralized reputation management in P2P networks. We depart from Eigen Trust, an algorithm designed for reputation management in file sharing applications over p2p networks. EigenTrust has been proved very effective against three different natural attacks from malicious coalitions while it performs poorly on particular attack organized by two different kinds of malicious peers. We propose various metrics of reputation based on ideas recently introduced for detecting and demoting Web spam. We combine these metrics with the original EigenTrust approach. Our mechanisms are more effective than EigenTrust alone for detecting malicious peers and reducing the number of inauthentic downloads not only for all the cases previously addressed but also for more sophisticated attacks. Copyright 2007 ACM

We present in this paper a secure and scalable Grid-based content management system for the management of high-volume multimedia data in the domain of the publishing industry. This is achieved by leveraging on existing individual solutions, such as the Alfresco content management system, the SRM standard for building scalable solutions based on the Grid and the GridTrust services for building trustworthy and secure Grid systems. Our solution brings closer the use of the Grid to the enterprise community within the context of a real world use case scenario. The solution facilitates the fine-grained usage control of the storage resources and a reputation-based matching between resource policies and users' past behaviour.

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