# Constraint graph

### From Glossary

Constraint graphs are used to conceptualize the set of constraints and their scopes in a CSP.

A *primal constraint graph* represents variables by nodes and associates an arc with any two nodes in the scope of in the same constraint.

A *dual constraint graph* represents each constraint with a node and associates a labeled arc with any two nodes whose scopes share variables. The arcs are labeled by the shared variables.