[lkb] Add a ranking module to LKB

[Stephan Oepen]

hi norman (and francis),

> > I want to add a ranking module to select the "best" scoped MRS
> > output. I'm not sure whether someone have done similar things
> > before.

  [...]

> There is code that selects the best parse based on the same model used
> by pet (i.e. looking at the derivation tree).

there was a fair amount of MaxEnt parse selection work (using the ERG
and other DELPH-IN grammars).  the code to rank LKB results is part of
the [incr tsdb()] add-on system.  regrettably (unlike the LKB proper),
[incr tsdb()] is not supported in SBCL.

however, all previous parse selection work in this context (for all i
know) was disambiguating syntactic ambiguity, i.e. derivations trees
returned by the parser (or generator).  hence, the problem of ranking
among the (potentially numerous) scope-resolved MRSs corresponding to
a single derivation remains unsolved at large.  i would expect that a
discriminative model, using structural semantic features, might be a
suitable approach, but it would require scope-resolved training data
(which is not part of the standard Redwoods treebanks) ...  i guess i
would view this as a potentially rewarding but not trivial project.

                                                     all best  -  oe

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