| Abstract |
The Semantic Web (SW) is an evolving extension of the World Wide Web in which Web content can be expressed not only in natural language but also in a format that can be read and used by software agents, thus permitting them to find, share and integrate information more easily. It comprises a variety of formally specified languages (RDF, RDF/S, OWL), associated formats (e.g. RDF/XML, N3, Turtle, N-Triples) and related technologies for their management.
Various platforms have been implemented in the recent years which apart from helping applications process Semantic data, evolve towards middleware services. These services are contacted remotely and provide controlled access to a repository on behalf of client applications, which are not needed to know or depend on the internal repository layout.
This thesis reviews such platforms and focuses on the design and implementation of the Semantic Web Knowledge Manager (SWKM) platform specifically. A common theme in these platforms is that they all need some sort of main memory representation of Semantic data, in order facilitate its processing internally. These representations are also used by externally in clients or on their own, to develop Semantic-aware applications. In this thesis we experimentally compared the performance characteristics of the main memory representation of each platform, by covering a multitude of possible access patterns. Additionally, we pay particular attention to the various Semantic versioning facilities, since versioning is an ubiquitous requirement for collaborative applications. In general, versioning is the process of assigning unique identifiers to states of artifacts and keeping other historical information and metadata. In this thesis, versioning services for the SWKM platform are introduced and compared to similar existing offerings.
In summary, the contribution of this work lies on the experimental evaluation and comparative analysis of various main memory representations of Semantic data, and on the design and implementation of middleware versioning services for Semantic models, offered as Web Services.
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Semantic Web Middlewares and Versioning Services
