Peer maintains a possession rule for each item in its index (subset if index is large)
Search strategy : a sequence of possession rules (with “hop counts”/search size limit)
Making this work:
“ Network ”: How to build overlay that supports possession rules
“ IR/DM ”: design search strategies that use possession rules (and work!)
Possession-rules overlays Index of P26 Rules/Items: Rule(A) Rule(B) Rule(C ) Rule(D) Peer26 P4,p5,p10 D P13,p15,p1 C P2,p6,p9 B P11,p7,p3 A Rule(item) neighbors item Example Search Strategy of P26: 2 hops in rule(A) 4 hops in rule(B) 6 hops in rule(C ) 4 hops in rule(A) 3 hops in rule(D)
Rules/Items: Rule(A) Rule(B) Rule(C ) Rule(D) Blind searching for O takes 13 probes Searching with rule( O ) takes 2 probes
When you find O , you often discover multiple peers that have O; when you give O , the searcher informs you of other peers with O .
Peers that have O can find other peers that have O
Coverage : The induced overlay on peers that satisfy each rule constitutes of large connected components.
Small degree : Each peer participates in a limited number of rules. (yet, overall there is a large number rules), for each rule it “participates” in, the peer maintains several participating neighbors.
Overlay and search boost each other (easy to find appropriate neighbors for each rule):
Network is “gnutella-like”, within each rule (… can use “super-peer” overlay within each rule !!)
Items belong to “topics.” There are very many topics; but each peer can only select items from a fixed set of topics. Topic popularities can highly vary; but each peer has equal interest in each of “its” topics.
We show that
RAPIER is at least as good as Prand
RAPIER is better than Prand when peers have fewer topics
Some rules are better than others (e.g., possession of a very popular item carries weaker information)
Unsuccessful search carries information : suppose you lost something, you think you lost it at home. You search home going through various closets and drawers and don’t find it, then you may decide to go search the office, even if you have not completed an exhaustive search at home. What happened? The posterior distribution on the item’s location had changed as a result of the search.
Take a sample of items currently in your index D , E , F , G .
“search” for these items in each possession rule you participate A,B,C
obtain a matrix: fraction of peers with item x in rule(y)
* 0.03 0.2 0.1 rule(C) 0.1 * 0.04 * rule(B) * 0.2 * 0.03 rule(A) G F E D Item Rule()
GAS strategy (example) C,C,C,A,C,C,A,C,A,C,B,B,A,C,B,B,C,A,B,B,C GAS search of size 21: 10 probes in rule(C) 6 probes in rule(B) 5 probes in rule(A) RAPIER search of size 21: 7 probes in rule(C) 7 probes in rule(B) 7 probes in rule(A) * 0.03 0.2 0.1 rule(C) 0.1 * 0.04 * rule(B) * 0.2 * 0.03 rule(A) G F E D Item Rule()