Robert A. Wagner
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Order-n correction for regular languages
A method is presented for calculating a string B, belonging to a given regular language L, which is “nearest” (in number of edit operations) to a given input string &agr;. B is viewed as a reasonable “correction” for the possibly erroneous string &agr;, where &agr; was originally intended to be a string of L. The calculation of B by the method presented requires time proportional to |&agr;|, the number of characters in &agr;. The method should find applications in information retrieval, artificial intelligence, and spelling correction systems.
Common phrases and minimum-space text storage
A method for saving storage space for text strings, such as compiler diagnostic messages, is described. The method relies on hand selection of a set of text strings which are common to one or more messages. These phrases are then stored only once. The storage technique gives rise to a mathematical optimization problem: determine how each message should use the available phrases to minimize its storage requirement. This problem is nontrivial when phrases which overlap exist. However, a dynamic programming algorithm is presented which solves the problem in time which grows linearly with the number of characters in the text. Algorithm 444 applies to this paper.
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