Domain Views for Constraint Programming

Views are a standard abstraction in constraint programming: They make it possible to implement a single version of each constraint, while avoiding to create new variables and constraints that would slow down propagation. Traditional constraint-programming systems provide the concept of em variable views which implement a view of the type y = f(x) by delegating all (domain and constraint) operations on variable y to variable x. This paper proposes the alternative concept of em domain views which only delegate domain operations. Domain views preserve the benefits of variable views but simplify the implementation of value-based propagation. Domain views also support non-injective views compositionally, expanding the scope of views significantly. Experimental results demonstrate the practical benefits of domain views.