In our approach, metadata is the key to scalability. Metadata is used to characterize the data for several purposes, including query processing, browsing, and retrieval. Metadata may take different forms. We call our mediated architecture CAFE for Cooperating Agents Find Everything. In CAFE there are application agents and brokers.
Brokers are similar to application agents.
However, the data they manage is metadata, supplied to them by application agents and other brokers. Brokers are not necessarily organized in a strict hierarchy and sibling communication is allowed. The mean of the collected n -gram profiles of a set of documents is the centroid. Note that the centroid document isn't a real document. The whole corpus has a centroid as does any subset of member documents.