Abstract

The use of regular expressions to search text is well known and understood as a useful technique. It is then surprising that the standard techniques and tools prove to be of limited use for searching text formatted with SGML or other similar markup languages. Experience with structured text search has caused us to carefully re-examine the current practice. The generally accepted rule of "left-most longest match" is an unfortunate choice and is at the root of the difficulties. We instead propose a rule which is semantically cleaner and is incidentally more simple and efficient to implement. This rule is generally applicable to any text search application. 1 Introduction Regular expressions are widely regarded as a precise, succinct notation for specifying a text search, with a straightforward efficient implementation. Many people routinely use regular expressions to specify searches in text editors and with stand-alone search tools such as the Unix grep utility. A regular expression ...

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