18. The system of claim 17 , wherein the expansion module automatically expands the at least one constraint generates an expression that includes the at least one constraint and a further constraint that is automatically determined to correspond to the at least one constraint.
18. The system of claim 17 , wherein the expansion module automatically expands the at least one constraint generates an expression that includes the at least one constraint and a further constraint that is automatically determined to correspond to the at least one constraint. 23. The system of claim 18 , wherein the expansion module expands any one from a group of constraints including a search parameter constraint to any one from a group of constraints including, a category constraint, a keyword constraint, and an attribute constraint.