Eckhard Bick - VISL

(i.e., not too complex) derivational analysis, one that escapes the heuristic filters
described above. Research on large corpora can weed out the high frequency cases of
these words, which can then be entered into the lexicon. Checking against a 35
million word corpus, where I filtered the output of the parser for derived and
unknown words, I found only some hundred words (118 word form types) where a
derivative analysis had - wrongly - been preferred over the proper noun analysis. 33
Many instances were syntactically isolated in one-word headlines or brackets. 10
lexemes accounted for half the cases. Quite a few of these words had been given a
derivative analysis with very short or rare roots ('mar' for 'Maria', 'pá' for Paulo, 'the
chemical element 'frâncio' for 'Francisco', 'tê', 'fê' and 'zê'). Since I have a tag in the
lexicon () for non-deriving lexemes, it was easy to prevent these roots from
overgenerating. For others, like the group Cristiana, Cristiano, Cristina (root 'crista')
entering the names into the lexicon may be the appropriate solution.
It was not quantitatively possible to inspect the large corpus (especially
sentence initial words) for the opposite error, i.e. preferring a proper noun analysis
over a lexical derivational analysis, but shorter samples suggest that sentence initial
derived words are much less frequent than names. In mid-sentence, finally, the
contextual constraints are quite effective and likely to make the right choices.
A final, though, quantification on 21.806 words from the Borba-Ramsey corpus,
containing 452 (2.1%) of (real or supposed) name chains, yielded an error rate of 2%
for the PROP class (positive and negative errors combined, shaded in table 9). This
is higher than the parser's usual morphological/PoS error rate of under 1%, but one
must take into consideration that all 11 errors occurred heuristically, mostly with
lexically unknown words, of which half were spelled incorrectly.
(9) Table: name frequency statistics
correct analysis:
chosen tag:
Proper noun Other, simple Other, derived
PROP 79 (17.5%) 0 0
PROP 362 (80.1%) 2 (0.04%) 0
Other word classes 9 (2.0%) - -
The 2 cases of wrong positive choice were the sentence initial words Lagartixou
(which should have been a verb, derived from lagarto - 'lizard'), and Les (misspelled
for the verbal inflexion form Lês - of ler 'to read'). Of the 9 cases involving wrong
negative choices, 4 were names spelled in lower case (geraldinho, juraçy, sanhaço,
playboy), 2 were sentence initial words also occurring as common nouns (nogueira -
nut tree, and bezerra - 'female calf'), one was a place name (Santo Amaro, read as a
33 These statistics were done with an older version o the parser, which included ordinary lower case words in the prename
context. With the up-to-date version, there is not such a strong bias in favour of PROP readings, and the
percentage of false positive choices of a derivational reading might be expected to be somewhat higher.
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