Abstract

This paper classifies a family of grammar formalisms that extendcontext-free grammar by talking about tuples of terminal strings, ratherthan independently combining single terminal words into larger singlephrases. These include a number of well-known formalisms, such as headgrammar and linear context-free rewriting systems, but also a new formalism,(simple) literal movement grammar, which strictly extends the previouslyknown formalisms, while preserving polynomial time recognizability.The descriptive capacity of simple literal movement grammars isillustrated both formally through a weak generative capacity argument and ina more practical sense by the description of conjunctive cross-serialrelative clauses in Dutch. After sketching a complexity result and drawing anumber of conclusions from the illustrations, it is then suggested that thenotion of mild context-sensitivity currently in use, that depends on therather loosely defined concept of constant growth, needs a modification toapply sensibly to the illustrated facts; an attempt at such a revision isproposed.