This class class represents a rule formula control. It is not intended to be used directly. Specific phonological/morphological rules should extend this class. It is not abstract so that it can be modified in Windows Form designer. It is a button launcher with a rule formula view and a rule insertion control. It handles selection, deletion, insertion, and cursor movement for a rule formula. Rules that extend this class override the methods that provide information about the various table cells in the rule and the data contained in each cell.