11.14. Recommended Resources
Many examples of OOA-oriented system operation contracts can be found in Object-Oriented Development: The Fusion Method by Coleman, et. al. Object-Oriented Software Construction by Meyer shows many program-level contract examples in Eiffel. Within the UML, operation contracts can also be specified more rigorously in the Object Constraint Language (OCL), for which Warmer and Kleppe's The Object Constraint Language: Precise Modeling with UML is recommended.