🚀 go-pugleaf

Hi, everyone.  I'm in an introductory AI class this semester,
and we've been dealing with DCG's of late.  We're supposed
to write a query language that will be used to construct
Prolog queries to 5 databases.  My problem is not with
the DCG per se, but rather with handling 'variables', that
is variables in the query.
An example of a query would be:

retrieve country where Population > 1000.  

Note: that's thousands of thousands.  Anyway, I'm having
trouble figuring out how to handle Population and other
'variables'.  They're coming through as quoted atoms, as
expected.  Any ideas on how to turn this into a variable,
after determining the meaning?  Or am I taking the wrong
tack here?  This may be a really trivial problem, but I'm
fairly new to prolog, and I've been puzzling over this for
about 2 weeks.

Thanks,
Greg


""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
"  O softly singing lute, / See with my tears thou time do keep.           "
"  Yet softly, gentle strings, / Agree with love that cannot sleep.        "
"  Sorrow hyst whenas it sings. / When tears do fall then sighs arise.     "
"  So grief oft shines in most sad eyes, / Yea love through heart it dies. " 
"         -Francis Pilkington, 1624                                        "
"  Greg Martin  gmartin@cs.umr.edu          What disclaimer???             "