Peer-to-peer (P2P) data sharing is a valuable approach for sharing data among people when they are belonging to different institutions. There are strong demands on both flexible, high-precision search and protection of privacy at peer-to-peer data retrievals. Especially, it is demanded for searching relevant files in P2P environment by using metadata while the terms in metadata that are used in such queries and annotations include some private information. In this paper, I present a mechanism and an analysis of P2P-based semantic file sharing and retrieval that uses mobile agents. The mechanism enables us to utilize private ontologies for flexible concept-oriented semantic searches without loss of privacy in processing semantic matching among private metadata of files and the requested semantic queries. The private ontologies are formed on a certain reference ontology with differential ontologies for personalization. In my approach, users can manage and annotate their files with their own private ontologies. Reference ontologies are used to find out semantically relevant files for the given queries that include semantic relations among existing files and the requested files. Mobile agent approach is applied for both implementing a system with less use of network bandwidth and coding it into a set of simple and small programs. I show the effectiveness of the use of private ontologies in metadata-based file retrieval. Also I show that the mobile agent approach has somewhat less overhead in execution time when the network latency is relatively high, while it is small enough even when the network is ideally fast.
2012 by the Information Processing Society of Japan