I'm having a hard time tackling the following problem (perhaps some key data is missing). We have a constraint:$A+B= C$One is supposed to represent this one constraint using three binary constraints. Is this even possible? No domain is given, but even if it was, I really don't see how this could be achieved...
Contraint with three variables into three binary constraints
constraint satisfaction
Good question.  Your instinctive reaction is quite valid: if you stick with the variables $A,B,C$, there is no way to introduce some set of binary constraints that will be equivalent to $A+B=C$ (where each constraint is only allowed to mention two of $A,B,C$).The trick is to introduce new variables, or change the set of variables.  If you do that, it can be done.  For instance, see the reference that hengxin suggests: http://ktiml.mff.cuni.cz/~bartak/constraints/binary.html.  However, it would be understandable if you feel that this is in some sense cheating... which might be why you didn't think of this approach.