Eckhard Bick - VISL

6.5 A semantic Constraint Grammar
In the semantic, bilingual part of the Portuguese CG lexicon, meanings are expressed as
translation alternatives, and kept apart by listing - for each alternative - a set of
discriminators, - CG tags that are to be present in the final analysis for the alternative in
question to be chosen:
Portuguese word Danish translation to be chosen if tagged as
palavra ord1 tag1 tag3
ord2 tag1 tag5
ord3 tag2
ord4 tag4 tag5 tag6
In principle, all kinds of tags can be used as discriminators, e.g. semantic prototype
class and inflexion for nouns, valency, and subject class for verbs, semantic argument
class for prepositions etc. Comparing discriminator lists with actual tag strings, the
system goes for maximal discriminator instantiation. If palavra in the example has
received the tag string ‘tag1 tag2 tag5’, then ord2 will be chosen as the correct meaning
(translation).
As explained in chapter 6.3 and 6.4, the semantic module of my parser aims at
resolving bilingually motivated noun polysemy by disambiguating semantic prototype
membership. Rules can either target prototypes directly, or indirectly via atomic
semantic features. Chapter 6.5.1 discusses the techniques used to disambiguate atomic
semantic features, while chapter 6.5.2 is concerned with direct prototype
disambiguation. Chapter 6.5.3 explains how polysemy resolution can be achieved by
exploiting information that is not primarily semantic, such as morphosyntactic
information disambiguated at a lower level, and by the “instantiation” of valency
patterns.
6.5.1 Using feature inheritance reasoning
In the parser’s lexicon, every noun entry features a ‘±’ list for all 16 atomic semantic
features used in the system. This list is computed by a special program from the
prototype spectrum of the noun in question. Positive features are marked with capital
letters, negative features with small letters. Since the feature structures of a noun’s
semantic prototypes are compiled on top of each other, many atomic features of
polysemous nouns will appear as both positive (capital letter) and negative (small
letter). Consider the following examples of polysemous institution nouns, with their
Danish translation equivalents given according to semantic prototype inventory:
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