  We investigate the global GRAMMAR constraint over restricted classes of
context free grammars like deterministic and unambiguous context-free grammars.
We show that detecting disentailment for the GRAMMAR constraint in these cases
is as hard as parsing an unrestricted context free grammar.We also consider the
class of linear grammars and give a propagator that runs in quadratic time.
Finally, to demonstrate the use of linear grammars, we show that a weighted
linear GRAMMAR constraint can efficiently encode the EDITDISTANCE constraint,
and a conjunction of the EDITDISTANCE constraint and the REGULAR constraint
