Bookmark-driven Query Routing in Peer-to-Peer Web Search

We consider the problem of collaborative Web search and query routing strategies in a peer-to-peer (P2P) environment. In our architecture every peer has a full-fledged search engine with a (thematically focused) crawler and a local index whose contents may be tailored to the user's specific interest profile. Peers are autonomous and post meta-information about their bookmarks and index lists to a global directory, which is efficiently implemented in a decentralized manner using Chord-style distributed hash tables. A query posed by one peer is first evaluated locally; if the result is unsatisfactory the query is forwarded to selected peers. These peers are chosen based on a benefit/cost measure where benefit reflects the thematic similarity of peers' interest profiles, derived from bookmarks, and cost captures estimated peer load and response time. The meta-information that is needed for making these query routing decisions is efficiently looked up in the global directory; it can also be cached and proactively disseminated for higher availability and reduced network load