The advent of digital libraries along with the tremendous growth of digital content call for distributed and scalable approaches for managing vast data collections. Peer-to-peer (P2P) networks emerge as a promising solution to delve with these challenges. However, the lack of global content/topology knowledge in an unstructured P2P system demands unsupervised methods for content organization and necessitates efficient and high quality search mechanisms. Towards this end, Semantic Overlay Networks (SONs) have been proposed in the literature, and in this paper, an unsupervised method for decentralized and distributed generation of SONs, called DESENT, is proposed. We prove the feasibility of our approach through analytical cost models and we show through simulations that, when compared to flooding, our approach improves recall by more than 3-10 times, depending on the network topology.