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• Nouns and verbs can be guessed in the text on the basis of their
morphological properties; thus, separate rule-based guessers were developed, and
their results were manually corrected in the training corpus; and,
• The disambiguation of closed-class items in context is, to a considerable
extent, possible on the basis of rules similar to ‘local grammars.’ A certain amount
of ambiguities in the training corpus have to be dealt with manually.
In the remainder of this section, we report on tagset design (section 3.2); on an
architecture for the creation of a tagger lexicon and a training corpus (section 3.3);
and, on verb and noun guessing and the disambiguation of closed class items (sections
3.4 to 3.6).
3.2 Tagset Design
The tagset designed for Northern Sotho is organised as a logical tagset (similar to
a type hierarchy); this opens up the possibility to formulate underspecified queries to
the corpus.
The tagset mirrors some of the linguistic specificities of Northern Sotho, but is also
conditioned by considerations of automatic processability with a statistical tagger.
The tagset reflects properties of the nominal system of classes and concords: as they
are (mostly) lexically distinct, we introduced class-based subtypes for nouns, pronouns
and concords, as well as for adjectives: N, ADJ, C (for concord) and PRO (for pronoun)
have such subtypes. As concords and pronouns have functionally and/or semantically
defined subtypes, we apply the class-based subdivision in fact to the types listed in
Table 6:
Table 6: Nominal Categories that have Class-related Subtypes
N Nouns CPOSS possessive concords
ADJ adjectives EMPRO emphatic pronouns
CS subject concords POSSPRO possessive pronouns
CO object concords QUANTPRO quantifying pronouns
CDEM demonstrative concords
Given the complexity of the system of verbal derivation (cf. Table 3 above), an
attempt to subclassify verbal forms accordingly would have led to an amount of
tags (i.e., of distinctions) that would not be manageable with a statistical tagger.
Furthermore, as- according to Northern Sotho orthography conventions- concords,
adjectives and pronouns are written separately from the nouns and verbs to which
they are grammatically related (disjunctive writing), these elements receive their
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