In current Peer-to-Peer networks, distributed and semantic free indexing is widely used by systems adopting "Distributed Hash Table" ("DHT") mechanisms. Although such systems typically solve a. user query rather fast in a deterministic way, they only support a very narrow search scheme, namely the exact hash key match. Furthermore, DHT systems put a lot of responsibility to peers in terms of indexing and storage while neglects peer interests and actual capabilities. In this thesis, we propose an ontology based approach to construct the logical overlay for a P2P network. Our approach uses a global ontology as the basis of communications for all participants in the network, and peers can search from data, knowledge, and past experience from other peers, and build community of interest to better utilize the network resources. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]