A Taxonomy of Sublinear Multiple Keyword Pattern Matching Algorithms

This paper presents a taxonomy of sublinear keyword pattern matching algorithms related to the Boyer-Moore algorithm [BM77) and the Commentz-Walter algorithm [CW79a, CW79b). The taxonomy includes, amongst others, the multiple keyword generalization of the single keyword Boyer-Moore algorithm and an algorithm by Fan and Su [FS93, FS94). The corresponding precomputatioD algorithms are pre~ented as well. The taxonomy is based on the idea of ordering algorithms according to their essential problem and algorithm details, and deriving all algorithms from a common starting point by successively adding these details in a correctness preserving way. This way of prese~tation not only provides a complete correctness argument of each algorithm, but also makes very clear what algorithms have in common (the details of their nearest common ancestor) and where they differ (the details added after their nearest common ancestor). Introduction of the notion of safe shift distances proves to be essential in the derivation and classification of the algorithms. Moreover, the paper provides a common derivation for and a uniform presentation of the precomputation algorithms, not yet found in the literature.