Non-local scrambling: the equivalence of TAG and CCG revisited

It is well known that standard TAG cannot deal with certain instances of longdistance scrambling in German (Rambow, 1994). That CCG can deal with many instances of non-local scrambling in languages such as Turkish has previously been observed (e.g. by Hoffman (1995a) and Baldridge (2002)). We show here that CCG can derive German scrambling cases which are problematic for TAG, and give CCG analyses for other German constructions that require more expressive power than TAG provides. Such analyses raise the question of the linguistic significance of the TAG-CCG equivalence. We revisit the original equivalence proof, and show that a careful examination of the translation of CCG and TAG into Indexed Grammar reveals that the IG which is strongly equivalent to CCG can generate dependencies which the corresponding IG obtained from an LTAG cannot generate.