The varieties of mathematical basis for formalizing linguistic theories are more diverse than is commonly realized. For example, the later work of Zellig Harris might well suggest a formalization in terms of CATE-

This paper presents a sketch of a formal proof of strong equivalence, where both grammars generate equivalent parse results, between any LTAG (Lexicalized Tree Adjoining Grammar: Schabes, Abeille and Joshi (1988)) G and an HPSG (Head-Driven Phrase Structure Grammar: Pollard and Sag (1994))-style grammar converted from G by a grammar conversion (Yoshinaga and Miyao, 2001). Our proof theoretically justifies some applications of the grammar conversion that exploit the nature of strong equivalence (Yoshinaga et al., 2001b; Yoshinaga et al., 2001a), applications which contribute much to the developments of the two formalisms

Abstract not found

In early transformational grammar, lexical items were essentially lifeless, pushed around by powerful and diverse phrase structure rules and transformations. The balance of power began to shift, though, in the late 1970s. The phrase structure rules became more generalized (Jackendoff 1977; Gazdar et al. 1985; Kaplan &