Constraint-Based Approach to Language Processing

Centre for Language Technology, Macquarie University, Sydney, Australia.
3 February 2003

(Last Modified: Friday, 28 February 2003 9:17 PM)

This presentation is about an overview of a few papers around the works led by Philippe Blache, which all address the question of the adequacy of the notion of Constraint in Linguistics and in Computer Science.

On one hand we’ve got many modern linguistic theories that rely on the notion of constraints, and on the other hand we’ve got Constraint Logic Programming.

Thus when the time comes to implement a parsing process it seems very appealing to figure it as a Constraint Satisfaction process. However, the few attempts to do so are mostly using constraints in a passive sense and therefore don’t fully take advantage of constraint programming.

The bunch of papers I’m going to talk about show that a generative interpretation of the relation between language and grammar and an inappropriate representation of the linguistic information are the two main reasons that prevent the parsing process from being interpreted as an actual constraint satisfaction one.

A new approach is presented where all the linguistic information is specified and represented by means of constraints. The underlying formalism called Property Grammar is also discussed. Such a representation allows the parsing process to be interpreted as a pure constraint satisfaction program.

After a rather brief overview of some of the main theoretical points of interest I’ll be focusing on some practical examples of language analysis using a Property Grammar.

For references, the discussion will be based on the following papers:

1. Philippe Blache (2000). "Constraints, Linguistic Theories and Natural Language Processing", in Natural Language Processing, D. Christodoulakis (ed), Lecture Notes in Artificial Intelligence 1835, Springer-Verlag
2. Philippe Blache & Frank Morawietz. (2000). "A Non-Generative Constraint-Based Formalism", Research report, LPL.
3. Philippe Blache & David-Olivier Azulay (2002) "Parsing Ill-formed Inputs with Constraints Graphs", in A. Gelbukh (ed), Intelligent Text Processing and Computational Linguistics, LNCS, Springer.