Linguistic Modeling for Multilingual Machine Translation

2.2. MODULARITY 21
8 Morphological generation is done with the help of the external morphological
module mpro*. The surface string is generated from the basic lexeme
and the information about compounding, derivation and inection.
monotonicity
(23)
MSEN
The man is afraid of a sentence which cannot be pronounced.
The advantages of this straticational approach are the reduced complexity of
every submodule and the restriction of certain modules to specic functionalities.
One risk with this approach, however, is that some information might
not be accessible at a given level though necessary for unambiguous processing.
In the face of ambiguities at a given level, straticational systems produce a
number of possible structures which have to be ltered out at higher levels of
processing. This approach is not ecient ifthepoints where an ambiguity is
introduced and the point where it is resolved are distant (cf. [Mehrjerdian92]).
A second problem with this approach is the possible incompatibility at dierent
levels due to the nonmonotonicity introduced by dierent strata. In order to
maintain the advantages of the straticational approach, thereby reducing to a
minimum the risks incurred, a static modularity isintroduced in CAT2 which
operates orthogonally on the stratication modules.
2.2.2 Static Modularity
In order to assure unambiguous processing at every straticational level, every
type of information should in principle be accessible throughout all levels. As
the main data come from the lexicon, the lexicon should be present atevery
level, supplying the levels even with those types of information which are not
typically required at that level. Ambiguities at one level (e.g. dierent syntactic
and semantic properties of the verb to be) should be represented so as not to
create an overgeneration at a level where these ambiguities are not relevant (e.g.
the morphological level). As CAT2 uses one lexicon to which there is access
at every level for each type of information, semantic information can already
be used at level CS in order to exclude spurious objects, or morpho-syntactic
information can be used in generation at an early stage in order to speed up
generation. In order to ensure the consistency of the lexicon and the grammar
modules, a language declaration system, including a feature declaration system
and a macro system are employed.