PDF (Online Text) - EURAC

oriented dictionary that would explicitly store such properties. As far as the corpus
is concerned, a multilevel annotation would be more appropriate than the current
monodimensional view: without changes to the current annotation, extra layers
may be added for the above-mentioned features of nouns and verbs, but also for an
appropriate treatment of fused forms (cf. dirang, ‘do what?’ from dira + eng) and of
multiword items, for example, idiomatic expressions (cf. bona kgwedi ‘see the moon’
i.e., ‘menstruate’). As Northern Sotho orthography is not yet fully standardised, a
distinction between standard orthography and observed (possibly deviant) orthography
may be introduced through additional layers.
5. Conclusions and Future Work
We reported on an ongoing research and development project for the creation
of tagging resources for Northern Sotho. In this context, modular components of a
two-layered architecture were created, which are needed in the first place for the
preparation of a training corpus for statistical tagging, but which will prove equally
useful, we hope, for the later development of larger corpora.
We bootstrap the training corpus and the tagger lexicon in parallel, using semi-
automatic procedures consisting of a rule-based automatic pre-classification and
subsequent manual validation: the procedures concern the identification of verbal
and nominal forms and the disambiguation of closed class items. These procedures are
applied one after the other by order of their expected precision (‘easy-first’, ‘safety-
first’), leading thereby to a partly disambiguated corpus. For the creation of the
training corpus, the remaining ambiguities are removed manually, whereas this task is
supposed to be left to the statistical tagger in the later creation of larger corpora.
Linguistic knowledge about the language is extensively used in the definition of the
automatic procedures: morphological and morpho-syntactic regularities in the local
context provide the starting point for their formulation.
Future work on the tools described in this paper will be devoted to the development
of further disambiguation rules, to the finalisation of a fully disambiguated training
corpus, and to tagger training and tests. This will allow us to (i) assess tagging quality
as obtained by the use of the statistical tagger only in a setup with our rule-based
pre-processing, (ii) to stabilise the proposed tagset on the basis of experience with
statistical tagging, and (iii) to undertake tagging of the PSC, which could then serve
for lexicographic exploration.
A well-designed POS-tagger for Northern Sotho would provide a flying start to the
development of similar taggers for the other Sotho languages, the Nguni languages,
112