In this thesis, we study approximate pattern matching problems. Our study is based on the Levenshtein distance model, where errors considered are 'insertions', 'deletions', and 'substitutions'. In general, given a text string, a pattern, and an integer k, we want to find substrings in the text that match the pattern with no more than k errors. The pattern can be a fixed string, a limited expression, or a regular expression. The problem has different variations with different levels of difficulties depending on the types of the pattern as well as the constraint imposed on the matching. We present new results both of theoretical interest and practical value. We present a new algorithm for approximate regular expression matching, which is the first to achieve a subquadratic asymptotic time for this problem. For the practical side, we present new algorithms for approximate pattern matching that are very efficient and flexible. Based on these algorithms, we developed a new software tool called 'agrep', which is the first general purpose approximate pattern matching tool in the UNIX system. 'agrep' is not only usually faster than the UNIX 'grep/egrep/fgrep' family, it also provides many new features such as searching with errors allowed, record-oriented search, AND/OR combined patterns, and mixed exact/approximate matching. 'agrep' has been made publicly available through anonymous ftp from cs.arizona.edu since June 1991.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/185914 |
| Date | January 1992 |
| Creators | Wu, Sun. |
| Contributors | Manber, Udi, Myers, Eugene W., Kannan, Sampath, Myers, Donald |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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