Concept maps are used in a wide variety of disciplines because of their ability to make complex information structures explicit. Concept maps can be used informally or formally -- where the graphical "syntax" of the maps is tightly controlled. Both forms are needed. Constraint Graphs is a program in which users can constrain arbitrary graphs to conform to any of a wide variety of graphical formalisms. The Constraint Graphs program is combined with a graphical user interface to yield an interactive concept mapping system, that can transcend informal concept mapping and many concept mapping formalisms.