| Abstract |
One of the most important aspects in computer science is the management of data. Web services provide an infrastructure for distributed computing at large, independently of any platform, system or programming language. Peer-based architectures, in which resources are shared by direct exchange between systems, offer a significant advantage and can be the base of the scalable data integration.
Data and actions that are represented through web services should be described, offering ways for automating the processes. The discovery of the appropriate services should be depended on logic-based formalizations in order to enhance their functionality and improve their proper matching. Moreover, the issue of the composition of web services is of major significance as it relies on the composition of existing business services into new and more complex services. A major limitation of the web services technology is that finding and composing services still requires manual effort. The increasing number of web services surcharges the previous limitation.
The evolution of semantic web services in addition with the development of newly frameworks has given powerful means for dealing with the previous challenges. Active XML will be presented, a new idea which having as its base the combination of XML and web services provides a simple and unified platform for the management of such active data. The combination of them appoints the suitable framework for distributed management of information. AXML is a language that empowers web services to achieve data integration by embedding calls to other web services and is structured over a peer-to-peer architecture. Thus, it is obvious to use these means having as priority to succeed in formalizing the mentioned challenges in a more automatic way.
This thesis proposes a framework that sets an interaction-based approach at the communication of peers, through the use of service calls. Its main advantages are the existence of different roles for every peer and the dynamic way that impose in the composition process. The presence of AXML serves the notion of active data as a means of communication between peers, adding efficiently the periodical activation and materialization of service calls. Specifically, the concept of the implicit call in AXML documents is introduced and a technique for discovering and composing web services in a role-based p2p network is described. The elements that are necessary for AXML documents in order to enhance the description of the embedded services are presented, supporting the use of OWL-S descriptive characteristics. Moreover, the structure of such a network and the way of its development is presented, outlining all the characteristics and the way of involvement of its peers. The whole methodology, advancing the functionality that AXML provides, set a clear layout for data integration.
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P2P service provisioning in the AXML framework
