A system that provides a visual mechanism (e.g., user interface (UI)) by which a user can design a regular expression is provided. The graphical interactive mechanism enables a user to develop regular expressions without an understanding of the intricacies of the regular expression syntax. The UI can provide an interactive mechanism by which a user can graphically annotate (e.g., color, highlight) a regular expression thus, mapping the expression to a particular tabulated output. The novel UI can provide a particular kind of dialog layout with several controls and dynamically linked views, e.g., a data view, a regular expression view and a column view which can facilitate definition of the regular expression as well as creation of mappings to output columns (e.g., annotations).