Hi,
I can give you some more information on the topic:
pFusion: A P2P Architecture for Internet-Scale Content-Based Search and Retrieval
Internet-scale systems for sharing resources, including files and documents can be created by the use of the emerging Peer-to-Peer (P2P) model. It has become an attractive and powerful paradigm. The fact that nodes are typically located across different networks and domains hinders the process of information retrieval efficiently. This article describes the effect on the keyword search algorithms the effects of topologically-aware overlay
construction techniques. The pFusion (Peer Fusion) architecture presented here is aimed at the efficient integration of the information that is scattered among the different peers in different geographical area. It has been built on the work in the work in unstructured peer-to-peer systems. only local knowledge is used by the system.

Full report:
http://citeseerx.ist.psu.edu/viewdoc/dow...81E?doi=10.
http://cgi.di.uoa.gr/~charnik/files/pFusion.pdf