Context-Free Representational Under specification For NLG
The purpose of the COGENT Project1 is to look at issues in generic (wide-coverage and reusable) surface generation.
Central to generic generation is the issue of nondeterminism, i.e. multiple outputs for the same input, and how to control
it. Nondeterminism arises from three main sources in natural language generation2:
(i) wide syntactic and lexical coverage: the wider the coverage of grammar and lexicon, the more word strings can be generated from the same
semantic representation;
(ii) underdetermined inputs: the less specific the semantic or conceptual representation, the
more word strings correspond to it; and
(iii) unconstrained mapping from inputs to realisations: the fewer constraints
(e.g. rule application conditions, intermediate selection processes, probabilities) there are, the more realisations can
be generated from an input. Wide coverage and (even extensively) underdetermined semantics can both make an NLG
system more generic, because they help make a system more portable and reusable. However, at present no comprehensive
methodology for controlling the nondeterminism, for deciding between alternatives, exists. It is one of the
core aims of COGENT to develop such a methodology.
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