Eckhard Bick - VISL

particular, mapping rules may - at least within the current cg-compilers - only refer to
pre-existing tags, i.e. morphological tags which have all (or nearly all) been
disambiguated already, not to syntactic tags introduced by other mapping rules (which
ordinarily would be highly ambiguous). Therefore, C-contexts are redundant and very
rare in mapping rules. For the same reason, in syntactic disambiguation rules, too, all
contexts referring to morphological information do not usually need C-tags. And even
for syntactic tags the C-option has a handicap: the double tags used for words bearing
clause function, which cannot be AND-grouped in the current compiler’s set-definitions
(both cg1 and cg2 allow only OR-grouping for syntactic tags).
(b) The C-percent parameter is higher for right hand positions than for left hand
positions, and lowest for the zero position. Left hand contexts are more common than
right hand contexts of the same distance, and the disparity increases with distance,
from ca. 50% for the +1/-1 pair (1636 and 2250 rules, respectively) to 400% for the
most distant contexts.
It is quite hard to find a clear and general explanation for this interesting finding.
It seems to imply that for disambiguation, left hand context is more important (or easier
to use) than right hand context, and that left-looking rules can be applied before rightlooking
ones, since the latter would have to wait for the creation of safe right-hand
contexts by left-looking rules.
The real reason may even be a psycholinguistic one: Language has evolved as
speech, and is therefore processed in a linear way. It will therefore be a
communicational advantage, if the listener be able to anticipate the next word or word
group, or at least its type and function. Empirical priming tests and the existence of the
linguistic garden path problem seem to indicate that, in fact, humans tend to choose that
reading for a word that is suggested by its left hand context. So a right hand context has
to be "extra safe" in order to be allowed to make a difference.
Since Portuguese valency structures reflect this left-to-right approach, on the
syntactic level, where word classes are unambiguous, and functions are ambiguous,
arguments can be identified by finding a word of the relevant head word class to the
left, like in the case of an ambiguous @ACC after VFIN, or @P< after PRP. In the
morphological module, with its more local (narrower) rule scope, (group level)
modifiers are more important than (usually clause level) arguments, and it seems logical
that articles, determiners, numerals and intensifiers (which all typically precede their
head in Portuguese) are more essential to the type of head 122 they attach to, and “need”
their head more, than adjectives and prepositional phrases which as modifiers usually
come to the right of their head, and could be non-group, clause level constituents
(predicatives or adverbials). This explains the natural dominance of left hand contexts
122 Left context determiners, article determiners and numerals help recognize (disambiguate) nouns, immediate left context
intensifiers help recognize adjectives and adverbs.
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