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PrefixSearch

PrefixSearch use the prefix of Q of length w, and the ST-index to search for data subsequences that match the prefix of Q within tolerance ε

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PrefixSearch

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  1. PrefixSearch • use the prefix of Q of length w, and the ST-index to search for data subsequences that match the prefix of Q within tolerance ε • [Lemma 2] If two sequences S and Q with the same length l agree with tolerance ε, then any pair (S[i:j],Q[i:j]) of corresponding subsequences agree within the same tolerance: D(S,Q) ≦ ε D(S[i:j],Q[i:j]) ≦ ε, 1 ≦i ≦j ≦ l proof:

  2. MultiPiece • [Lemma 3] If Q and S with the same length p*w agree within tolerance ε, then at least one of the pairs (qi,si) of corresponding subsequences agree within tolerance ε/√p: where V indicates disjunction. proof: By contradiction. Let and where 0≦i < p-1

  3. Compare PrefixSearch and MultiPiece • w.r.t the volume they require in an f-dimensional feature space • PrefixSearch: , K is a constant • MultiPiece yields p spheres, each of volume proportional to , for a total volume of • MultiPiece is likely to produce fewer false alarms, and therefore better response time than PrefixSearch, where f>2.

  4. Project for Group 3: (Due 6/4) • 探討將subsequence matching的方法應用在2D-image 的快速查詢比對;提出其困難處及解決之道. • Project for Group 6: (Due 6/4) • 探討R-tree及其變形,並參考論文[FRM94],就trail之分割方式及其對查詢的影響提出報告. • Project for Group 7: (Due 6/4) • Study the techniques of video editing; consider various special effects and discuss the ways to detect shot changes under these effects using the mask-matching approach we discussed in class.

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