Eckhard Bick - VISL

(1) number of CG rules containing at least one valency context condition
Morphological rules Syntactic rules
"safe" heuristic "safe" heuristic
verbal valency 17.3% 10.0% 29.8% 28.4%
nominal LP
valency
6.5% 10.9% 4.8% 3.4%
"left valency"
1.5% 3.0% 1.4% -
It can be seen, that, on the whole, verbal valency is quantitatively more important to
disambiguation than nominal valency, which is not surprising given the fact that all
verbs receive valency information, while the figure for nouns and adjectives is only
10% for nouns and 7% for adjectives 117 . In analogy with what is said about the
distribution of "global" vs. "local" rules in chapter 3.7.3, verbal valency information is
used in a third of all syntactic rules, but only in one sixth of all morphological rules.
Since heuristic morphological rules are most likely to lack global contexts altogether,
they will obviously also be the ones least likely to make use of verbal valency, since the
dependencies concerned cannot be guaranteed to be contiguous. In contrast, syntactic
rules need verbal valency information even if they are heuristic (the percentages for safe
resp. heuristic syntactic rules are nearly the same).
Nominal valency and left valency, on the other hand, since they are about group
structure and lexical neighbourhood, are primarily used for close context morphological
disambiguation, a rationale that becomes even clearer for heuristic morphological
disambiguation.
Quite another aspect of the valency discussion are semantically motivated
selection restrictions. At present, the parser lexically assigns unambiguous
±HUM/ANIM head tags to 35.7% of all adjectives, and ±HUM/ANIM subject tags to
48.2% of all verbs in running newspaper text:
verb with obligatorily human subject ('discutir' - ‘to discuss’)
verb with obligatorily inanimate subject ('explodir' - ‘to explode’)
verb with obligatorily animal subject ('coaxar' - ‘to croak‘)
verb with obligatorily plant subject ('espigar' - ‘to sprout’)
adjective with obligatorily human head ('assassudo' - ‘wise’)
adjective with obligatorily inanimate head ('asséptico' - ‘sterile’)
117 These are token frequency related numbers for disambiguated running newspaper text. In the PALAVRAS lexicon, the
percentage of nouns and adjectives featuring valency information is lower, since many very infrequent nominals lack
valency patterns.
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