Appendix B. The Object Constraint Language

The Object Constraint Language 2.0 (OCL) is an addition to the UML 2.0 specification that provides you with a way to express constraints and logic on your models. For example, you can use OCL to convey that a person's age must always be greater than 0 or that a branch office must always have one secretary for every 10 employees.

OCL isn't new to UML 2.0; it was first introduced in UML 1.4. However, as of UML 2.0, it was formalized using the Meta-Object Facility and UML 2.0. From a user's perspective the language has been updated and refined but the fundamentals remain the same. This appendix introduces the basic concepts of OCL. For more detailed information, consult the OCL specification available from the Object Management Group's web site (http://www.omg.org/).