[developers] smallish native DMRS grammar

[Ann Copestake]

I have just checked in to the LKB svn repo a small grammar - dmrscomp - 
and some code that extracts simple DMRSs directly from the feature 
structures produced by that grammar rather than going via MRS and RMRS.  
This is based on the mrscomp grammar (though with some clean up and 
minor extension) - there's a fairly detailed README file.  There are a 
fair number of items on the TO-DO list - possibly the most 
time-consuming one would be to make the generator code work with this 
grammar, not because there's any big problem (that I can think of) but 
because the generator is quite complicated.  There is also a promise of 
more detailed notes, which I will supply relatively soon, I hope - this 
was an interesting exercise in thinking through semantic composition.

If someone would like to collaborate on trying a similar exercise with a 
larger grammar, I'd be very interested.  It would help if it were a 
grammar which already had the characteristic variable property, in which 
case I think the main part of the conversion should be fairly easy.

There are a number of potential advantages in constructing DMRS 
directly, including the ability to construct a DMRS forest directly from 
a parse forest.  I would argue that it also enforces some notions of 
semantic well-formedness more directly than is possible with MRS - 
obviously including the (equivalent of) characteristic variable 
property.  The semantic `fingerprint' of constructions can be expressed 
more simply, because DMRS removes much of the redundancy of MRS.  But, 
of course, this is only interesting if we really can express everything 
we want to with DMRS.

All best,

Ann