We show how multicomponent TAGs, although in their “local” version equivalent to “simple” TAGs, enable one to associate the derived structures with a richer set of derivations. This is especially useful for representing some nonlocal dependencies such as wh‐extraction out of NP or extraposition, as soon as one interprets the derivation structures as representing the predicate‐argument dependencies. However, there is a formal alternative in the formalism of synchronous TAGs that achieves a similar result, namely, that associates standard syntactic derivations with nonisomorphic semantic derivations, and relies on the latter to represent the dependency relations. We show that the latter treatment accounts for a different range of extraposition facts in French, where the relationship between the head noun and its extraposed dependent is a semantic one. Nous montrons comment les TAGs ensemblistes “locales” (MCTAGs), qui sont équivalentes aux TAGs simples, permettent ?associer aux structures syntaxiques dérivées un ensemble plus large de structures dérivationnelles. Cela est particulièrement utile pour la représentation des dépendances non locales qu'on observe dans les extractions hors du groupe nominal et les extrapositions, à partirdu moment oùľon interprète les arbres de dérivation comme représentant les relations de dépendance. II existe toutefois une autre possibilityé dans le cadre des TAGs synchrones qui associe aux dérivations syntaxiques standard des dérivations sémantiques non isomorphes et interprète les relations de dépendance en se basant sur ces dernières. Nous montrons que cette deuxième possibilityé est mieux adaptée pour des cas ?extraposition en français où la relation de dépendance entre le nom těte et ľélément extraposé est ?ordre sémantique.

Taking examples from English and French idioms, this paper shows that not only constituent structures rules but also most syntactic rules (such as topicalization, wh-question, pronominalization ...) are subject to lexical constraints (on top of syntactic, and possibly semantic, ones). We show that such puzzling phenomena are naturally handled in a 'lexicalized' formalism such as Tree Adjoining Grammar. The extended domain of locality of TAGs also allows one to 'Jexicalize' syntactic rules while defining them at the level of constituent structures.