A constraint Block is a subtype of a Block. It is a class stereotyped with «ConstraintBlock». It has a constraint with an expression to constrain the values of its constraint parameters. If an object initialized from a constraint Block and a value bound to a constraint parameter of that object is changed, Cameo Simulation Toolkit will evaluate the expression of the constraint. You can see more information about how Cameo Simulation Toolkit evaluates an expression in Evaluating expressions.