Eckhard Bick - VISL

2.2.5 Tagging categories: word classes and inflexion tags
2.2.5.1 Defining word classes morphologically
The parser's tag set contains 14 word class categories, that combine with 24 tags for
inflexion categories, yielding several hundred distinct complex tag lines. Thus, in the
tag-line 'V PR 3S IND VFIN', for example, the word class 'V' alternates with 12
other word classes, and within the V-class 'PR' (present tense) alternates with 5 other
tenses, each of which comes in 6 different shades of person-number combinations,
for both 'IND' (indicative) and 'SUBJ' (subjunctive). This way 6x6x2=72 finite verb
forms can be described by using only 6+6+2=14 "partial" tags. This analytical
character of the tag strings makes them more "transparent", and it also makes things
easier for the disambiguation rules. In contrast to other systems (cp., for example, the
CLAWS-system, as described in Leech, Garside, Bryant, 1994), a clear distinction is
upheld in the tag string between base forms ("words"), word classes and inflexion
categories.
Furthermore, word classes are almost exclusively defined in morphological
terms, thus keeping them apart from the syntactic categories 52 . A noun (N), for
instance, is defined paradigmatically as that word class, which features gender as
(invariant) lexeme category and number as (variable) word form category. The
opposite applies to numerals (NUM), while both gender and number are lexeme
categories for proper nouns (PROP), and word form categories for adjectives (ADJ).
Pronouns can be classified along the same lines, yielding a determiner class
(DET) with the same (variable) categories as adjectives, and a "specifier" class
(SPEC) of "noun-like" pronouns featuring the same (invariant) categories as proper
nouns. Personal pronouns (PERS), a third class, has 4 word form categories: number,
gender, case and person. All three pronoun classes are distinguishable from the
"real" nominal classes by the fact that they do not allow derivation (a typical
characteristic of deictics).
Pronouns like 'o' and 'este', that can appear in both "adjectival" and "nounlike"
position, are in my system unambiguous members of the DET-class, as judged
by the exclusively morphological criterion of inflexional variability with regard to
number and gender. The article class doesn't receive special treatment either: 'o' is
always 53 DET, whether used as "article", "adjectival demonstrative" or "noun-like
demonstrative". (Secondary) tags for and do appear in the tag list, but
they are not word class categories, and are therefore only disambiguated at a later
stage (the valency level of CG), for use in the MT module.
Among participles, the word class world's enfants terribles, only the past (or
perfective) participle (V PCP) is inflexionally productive in Portuguese, and I treat
52 I owe the urge to define word classes as morphologically as possible to Hans Arndt, who advocates a strict distinction
between decontextually defined (primary) tags and distributionally defined syntactic tags in corpus annotation,
suggesting category inventory as a means of word class definition in Danish (Arndt, 1992).
53 that is, if it is not the personal object pronoun 'o' or the letter name 'o', or the chemical abbreviation 'O'.
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