[developers] Valid MRS? Bug in ERG?

[Stephan Oepen]

hi mike and alexandre,

> Regarding conversion to EDS, the LKB goes to greater lengths to give an EDS even for ill-formed MRSs, while PyDelphin tries to avoid grammar-specific solutions. The result is that PyDelphin will, I think, apply predicate-modification more broadly than the LKB, but it is a bit more brittle.

conceptually, i think all MRSs should be converted to EDSs, and no
information that can be expressed in the EDS graph should be lost.
more practically: each EP (and each ICONS) in the MRS should introduce
a node into the EDS, and each semantic role whose value is associated
with a node should yield an edge (additional edges should be
introduced for instances of predicate modification).  additional or
illformed information in the MRS (e.g. invalid handle constraints or
roles whose value does not correspond to the label or intrinsic
variable of an EP) should be ignored.

on this view, conversion to EDS should always succeed.  indeed,
robustness to (linguistically) illformed MRSs has been a key goal in
the original EDS converter that is part of the LKB.  i would welcome
bug reports, in case you encounter conversion errors.

mike. why would you think any of the above might call for
grammar-specific solutions?  i would like to encourage pyDelphin to
embrace the same robustness goals as the LKB-based converter.  EDSs
were originally invented for practical utility, to make it easier for
downstream applications to work with ERG analyses; for that goal, any
MRS that comes out of the parser should also yield an EDS, no matter
its structure or contents.

best wishes, oe