Beta looks like a tool that does term rewriting, extended with a state machine to choose which grammar. From the document: The Beta program first reads in the

Beta looks like a tool that does term rewriting, extended with a state machine to choose which grammar. From the document: The Beta program first reads in the rules and then performs the transformations to the input data as defined by the rules. Beta rule grammars may be written to perform various kinds of tasks, including data conversion, extracting interesting examples out of text data, modelling morphological structures or processes and selecting correct readings of ambiguous word tokens and parsing surface syntactic structures of sentences. Thus, the Beta program can be used both for tasks for generating and for analyzing linguistic expressions.