Eckhard Bick - VISL

8.2 CG Progressive Level Parsing:
General conclusions
There does not appear to be any obvious limit as to which level of grammatical
distinction can be handled by Constraint Grammars. Rather, performance depends on
the amount and type of information available from the lexicon, and on the quality of
tags disambiguated on the preceding (lower) level(s) of analysis.
For example, identification of direct objects (@ACC) is rather difficult with
only (undisambiguated) morphological information to draw upon, as is the case
when morphological CG rules try to PoS-distinguish the Portuguese accusative
pronoun ‘a’ (to the left of an N/V-ambiguous word) from the determiner ‘a’ and the
preposition ‘a’. The task turns easier if lexical information about transitive valency is
provided, and after verbs, for instance, have been PoS-disambiguated: (NOT 1 )
suggests ‘a’ is not a pronoun, and (1C VFIN) is a very strong context condition for
discarding the determiner and preposition readings. The simultaneous treatment,
finally, of the @ACC tag together with other syntactic tags (like other @ACC
objects, or @SUBJ subjects etc.), allows a high degree of correctness: for example,
the uniqueness principle can be exploited by adding the context conditions (i) (NOT
*1 @