«takes as input a sequence of phrase-structure trees and modifies their labels according to a set of rules. ... Its rule notation is flexible enough to emulate head/argument-finding rules»
S. Riezler, J. Kuhn, D. Prescher, and M. Johnson. ACL '00: Proceedings of the 38th Annual Meeting on Association for Computational Linguistics, page 480--487. Morristown, NJ, USA, Association for Computational Linguistics, (2000)