Deductive parsers for LFG?
Mark_Johnson at Brown.edu
Mon Nov 28 13:40:47 UTC 2005
There are a number of excellent implementations of LFG around (including
the one from Parc, of course), but that is not what you're asking about.
The main reason why there are no deductive parsers for LFG is that LFG
has always been thought of in terms of satisfiability of constraints,
rather than deductive inference from a set of axioms and inference
rules. As far as I know there's no principled reason why this should
not be possible (c.f. my comment about finite satisfiability being
equivalent to deduction below), but it just hasn't been done.
There are technical issues to be solved, of course. Some are quite
theoretical: e.g. first-order deduction is Turing complete, while
first-order satisfiability is co-Turing complete (but LFG generally
requires the satisfying models to be finite, and first-order finite
satistfiability is Turing complete, just like deduction, see my "Two
Ways of Formalizing Grammars" in Linguistics and Philosophy 1994, which
actually discusses LFG parsing).
And there are practical problems in implementing a deductive parser for
LFG which stem from the multiple levels of representation and diversity
of constraints in LFG; arranging to coordinate these in a moderately
efficient manner is complicated!
John Colby wrote:
> Does anyone know of deductive parsers for LFG, whether described as
> per Shieber et. al (1994, 1995) or as parsing schemata as per
> Sikkel(1993, 1997)
> Thank you,
> *John E. Colby*
> *Ph.D. Candidate in Computer Science*
> *Baskin School of Engineering*
> Baskin Engineering Building
> University of California, Santa Cruz
> 1156 High St.
> Santa Cruz, CA 95064
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the LFG