Regular expressions with numeric occurrence indicators are an extension of traditional regular expressions, which let the required minimum and the allowed maximum number of iterations of subexpressions be described with numeric parameters. We consider the problem of testing whether a given regular expression E with numeric occurrence indicators is 1-unambiguous or not. This condition means, informally, that any prefix of any word accepted by expression E determines a unique path of matching symbol positions in E. The main contribution of this paper is a polynomial-time method for solving this problem, and a formal proof of its correctness.
Structured texts (for example dictionaries and user manuals) typically have a hierarchical (tree-like) structure. We describe a query language for retrieving information from collections of hierarchical text.
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