Eckhard Bick - VISL

Portuguese non-name words. Apart from that, the ambiguity distribution is almost the
same as in the mixed Borba-Ramsey Corpus (where the portion of unanalysed
Portuguese words is higher, 0.2-0.3%, due at least in part to scientific and dialectal text
contributions).
In 1.6% of all cases, a PROP tag was applied heuristically, - to capitalised words
that could not be given another analysis without orthographical change (in mid
sentence), or even after orthographical alteration (sentence initially).
3.2.2 Word class specific morphological ambiguity
In order to know where the CG-rules could be made to be most effective, or, in other
words, for which cases it was worth the trouble to write a lot of rules, I was interested in
getting a more detailed picture of Portuguese morphological ambiguity. For the closed
word classes (PRP, KS, KC, IN, DET, SPEC, PERS, NUM) ambiguity classes can be
taken directly from the lexicon, and it would in principle be possible to write rules for
every single word. For the open word classes (N, ADJ, PROP, V, ADV 76 ), however, a
statistical approach seemed appropriate to assess the magnitude of the problem.
Table (1) shows the numbers for a 170.666 word VEJA newspaper corpus,
containing 121.170 words (71%) that are assigned at least one open word class reading.
The basis for measuring ambiguity was a version of the parser that uses certain 3 verbal
portmanteau tags not used in 3.5.1, as well as some word internal disambiguation (cp.
3.4). The resulting reduction in overall ambiguity from 2.0 to 1.7 has to be borne in
mind when comparing the word class specific figures below with the findings in 3.5.1.
I have split up the V class into finite verbs (VFIN) and three non-finite
subclasses, INF, GER and PCP, both because they show a syntactically completely
different behaviour, and because the non-finite classes with their well-defined ending
('ar/er/ir' for INF, 'ando/indo' for GER and ado/ido' for PCP) can be expected to show
their own, narrow ambiguity pattern. That the latter is quite distinct from that of finite
verbs, can be seen form the low numbers for VFIN-INF, VFIN-GER and VFIN-PCP
("verb internal") ambiguity, respectively. The somewhat higher figure for VFIN-INF is
due to the fact that the Portuguese infinitive can be inflected - yielding ambiguity with
future subjunctive readings.
(1) Table: PoS-ambiguity class frequencies
N ADJ VFIN INF GER PCP ADV PROP all ambiguous
PoS pairs
N 2188 9273 10959 766 6 2197 2057 1940 29386
ADJ 241 2369 113 9 2334 1168 916 16423
76 This class does contain both a kind of "closed subclass" and the open class in '-mente', but is here treated as one.
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