[developers] top-level cfrom/cto values in xml always -1

[Ann Copestake]

This looks like you're putting something in the PET specific code that belongs
more generally.  More specifically, it seems as though fs-to-mrs is analogous
to the functions in mrs/interface.lisp some of which are lkb specific, while
some are for the fine system.  So we have the various LKB interface functions
doing similar things to the fs-to-mrs in the pet-interface and also
return-mrs-info-string in interface.lisp.  All of these will potentially have
to be individually updated to do the `global' cfrom/cto.  Similarly, the
current PET specific fs-to-mrs duplicates code for treating different scopes.

This really needs tidying up.  I would suggest a generic version of fs-to-mrs
function in interface.lisp with the LKB or PET specific bits in
lkb-interface.lisp or pet-interface.lisp.  The generic function should have a
standard set of options for the different `types' of MRSs.  I am happy to write
this, but someone else needs to volunteer to check the PET interface.

One thing I need to know though is where the global cfrom/cto values come from
in PET and more importantly, what they are taken to mean.  When I agreed to
Francis's (I think) suggestion to put cfrom and cto at the top level of the
RMRS as well as on the individual relations, there was an assumption that these
were equivalent to something that could be extracted from the RMRS (i.e., cfrom
was the min of the cfroms while cto was the max of the ctos).  I assume from
what's discussed here that they are not part of the FS in PET, but what exactly
is the semantics?  e.g., if the input string has a space at the end, which is
stripped by the tokeniser, does the space end up counting for the global cto
value or not?

Ann