Most Recent Match Queries in On-Line Suffix Trees (with appendix)

TL;DR

This paper introduces an augmentation to Ukkonen's suffix tree algorithm enabling efficient online queries for the most recent pattern matches, applicable to sliding windows and Lempel-Ziv compression.

Contribution

It presents a novel augmentation to suffix trees supporting optimal-time recent match queries in online streams, with applications to sliding-window indexing and compression.

Findings

Supports optimal-time recent match queries in online suffix trees

Maintains indexing time within a logarithmic factor of string size

Applicable to sliding-window indexing and Lempel-Ziv compression

Abstract

A suffix tree is able to efficiently locate a pattern in an indexed string, but not in general the most recent copy of the pattern in an online stream, which is desirable in some applications. We study the most general version of the problem of locating a most recent match: supporting queries for arbitrary patterns, at each step of processing an online stream. We present augmentations to Ukkonen's suffix tree construction algorithm for optimal-time queries, maintaining indexing time within a logarithmic factor in the size of the indexed string. We show that the algorithm is applicable to sliding-window indexing, and sketch a possible optimization for use in the special case of Lempel-Ziv compression.