Eckhard Bick - VISL

7.4 Machine translation
7.4.1. A teleological judgement perspective
Since parsing is not an independent goal in its own right, different parsing schemes
should be judged not only in terms of inherent criteria, such as information content
and error rate, but also from a teleological perspective. Ultimately, the crucial user
based criterion will be which uses a certain parsing scheme is likely to be put to. We
have already seen that different syntactic notational systems have to match certain
theoretical backgrounds, like functional or generative grammar, and have different
uses in teaching (tags vs. PoS colour notation, word based “kryds & bolle” 245
function vs. tree diagrams). Likewise, corpora using tag based flat annotation are
easier to search with ordinary string manipulation tools than graphical trees.
From a machine translation perspective, the following traits of the
Portuguese Constraint Grammar parser seem relevant:
♦ Detailed, word order independent, function tags make it easier to transform
source language structure into target language structure, without too many
complicated transformation rules. Especially where languages like Portuguese are
involved, which - unlike English - permit a great deal of variation in the order of
clause level arguments.
♦ It is of great importance for polysemy resolution to know which of a word’s
potential valency patterns has been instantiated in a given clause or phrase, and
which semantic class fills a given valency slot. Therefore it is advantageous that the
parsing formalism can handle the disambiguation of valency tags, selection
restrictions and other lexicon derived (originally) secondary semantic tags in the
same fashion used for morphology and syntax at the lower parsing levels.
♦ The Constraint Grammar formalism can further be used for the context
dependent mapping and disambiguation of translation equivalents that are not listed
in the lexicon or not linked to specific secondary tags.
♦ The before mentioned underspecification, in Constraint Grammar, of certain
postnominals, co-ordination and free nominal adjuncts becomes an asset when seen
from a machine translation perspective: - First, a large part of these cases is “true
syntactic ambiguity”, which can only be resolved by the fully contextualised
listener/reader. - Second, some of these structural ambiguities (prepositional phrase
attachment and co-ordination) are fairly universal, i.e. language independent, so that
they can be preserved in translation. Making such ambiguity explicit would only put
an unnecessary burden on the intermediate levels of the translation module.
7.4.2. The Progressive Level approach in Machine Translation
245 “Cross & circle”, the icons used in Danish primary schools to denote the (often word based) functions of subject and
predicator.
- 432 -