A dynamic constraint solver for solving a constraint satisfaction problem network that includes a plurality of nodes and a plurality of constraints determines a cardinality for a set of sub-problems. The cardinality is a numeric domain that represents the minimum number of instances in a port. The solver determines if a number of identifiable instances of sub-problems is less than the minimum number of instances. The solver then causes a user interface to display the identifiable instances and a placeholder for each instance that is below the minimum number of instances and is not identifiable.