Two-dimensional filters for structured text

The paper introduces a method for defining filters for structured text. In the method, the text structure is originally defined by a grammar consisting of a set of productions; To describe the information interests, a two-dimensional template is first created interactively from the grammar to show the structure of a set of textual elements, at a chosen level of detail. The template depicts the hierarchical structure of the elements and indicates also optionality, alternatives, and iteration in the structure. Then, the template is filled by constraints and annotations. The constraints allow giving conditions to the content of parts, to the position of parts in an ordered set of parts, and to the number of parts obeying a specified property. In a compound filter, several templates are connected by annotations. The method is intended to be used as a theoretical framework for developing flexible and powerful graphical interfaces for filtering structured text. A prototype implementation is described. Copyright (C) 1997 Elsevier Science Ltd