Domain Views for Constraint Programming
This work addresses efficiency and implementation challenges for constraint programming practitioners, representing an incremental improvement over existing methods.
The paper tackles the problem of implementing constraints efficiently in constraint programming by proposing domain views as an alternative to variable views, which simplifies value-based propagation and supports non-injective views compositionally, with experimental results showing practical benefits.
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.