Symmetry in constraint satisfaction problems (CSPs) has been considered in two fundamentally different ways: as an operation preserving the solutions of a CSP instance, or as an operation preserving the constraints. To reflect these two views, we define solution symmetry and constraint symmetry. We discuss how these concepts are related and show that some CSP instances have many more solution symmetries than constraint symmetries.
David A. Cohen, Peter Jeavons, Christopher Jeffers