1 Interaction Grammars

Developing a core
Interaction Grammar
for French with XMG
Guy Perrier
LORIA, Nancy-université

1 - Interaction Grammars
•The starting idea is the metaphor of the chemical molecule (Tesnière
1934).
•Categorial Grammars integrated this idea as a principle of syntactic
composition.
•Interaction Grammars use the same idea with the notion of polarity.

1 - Interaction Grammars
•Syntactic trees are decorated with polarized features which express their
saturation state and their ability to interact.
oPositive features express available resources.
oNegative features express expected resources.
oNeutral features express properties that do not behave as resources.
oVirtual features need to combine with positive, negative or neutral features to be
realized.

1 - Interaction Grammars
•Unlike Categorial Grammars, Interaction Grammars are designed in a model-
theoretic framework and not in a generative-enumerative framework.
•A grammar is a system of constraints. Parsing a sentence reduces to a constraint
satisfaction problem: we have to find models satisfying a set of constraints which
represent information from the grammar and from the input sentence.
•Constraints representing the grammar are expressed as polarized tree descriptions
and the corresponding models are completely specified syntactic trees, verifying
saturation and minimality properties.

1 - Interaction Grammars
•Models can be computed by specifying the initial tree descriptions step by step, iterating
on the elementary operation of node merging.
•Node merging is guided by the need of saturating features: positive features must
combine with negative dual features and conversely; virtual features must combine with
positive, negative or neutral features having the same name.
•In a description, node merging entails constraint propagation, so that the process
amounts to a sequence of tree superimpositions guided by polarities.