A Metadata Model for Semantics-Based Peer-to-Peer Systems

Peer-to-Peer systems are a new paradigm for information sharing and some systems have successfully been deployed. It has been argued that current Peer-to-Peer systems suffer from the lack of seman-tics. The SWAP project (Semantic Web and Peer-to-Peer) aims at over-coming this problem by combining the Peer-to-Peer paradigm with Semantic Web technologies. In the course of our investigations it turned out that the nature of Peer-to-Peer systems requires some compromises with respect to the use of semantic knowledge models. In particular, the notion of ontology does not really apply as we often do not find a shared understanding of the domain. In this paper, we propose a data model for encoding semantic information that combines features of ontology (concept hierarchies, relational structures) with a flexible description and ranking model that allows us to handle heterogeneous and even contra-dictory views on the domain of interest. We discuss the role of this model in the SWAP environment and describe the model as well as its creation and access.