ESP-index: A compressed index based on edit-sensitive parsing

We propose ESP-index, a self-index based on edit-sensitive parsing. Given a string S, ESP tree is equivalent to a CFG deriving just S, which can be represented as a restricted DAG G. Finding pattern P in S is reduced to embedding the parsing tree of P into G. Adopting several succinct data structures, G   is decomposed into two bit strings and a single array, requiring (1+ε)nlogn+4n+o(n) bits of space, where n is the number of variables of G   and 0<ε<10<ε<1. The counting time for the occurrences of P in S   is in O((1/ε)(mlogn+occclogmlogu)log⁎u), where m=|P|m=|P|, u=|S|u=|S|, and occcoccc is the number of the occurrences of a maximal common subtree in ESP trees of P and S  . With the additional array of nlogu bits of space, our index supports the locating and extracting. Locating time is the same as counting time and extracting time for any substring of length m   is O((1/ε)(m+logu)).