Do you wonder how to add expressions and constraints to your UML and OO models? Well, Object Constraint Language is the answer!
The Object Constraint Language (OCL) is a language that enables you to describe expressions and constraints on object-oriented models and not only. An expression is an indication or specification of a value. A constraint is a restriction on one or more values of an object-oriented model or system.
For example, expressions usage in your UML model might be for: