Glossary of Unified Modeling Language Terms - O

O

• Object - a runtime instance of a Class. Objects are rarely shown on diagrams (because there are usually too many) unless they are used to illustrate some scenario, test, etc. Such Objects are often shown with the Attributes of the Class populated with sample data
• Object Constraint Language (OCL) - a declarative language for describing rules and constraints that apply to UML models
• Object diagram
• Operation - the signature of a Method of a Class; consists of the Operation Name, Visibility, Parameter list, Return Type, and Property-string
• Operator - an algorithmic feature of Interaction Frame that defines the behavior of that frame. Examples include:
  • alt - multiple alternatives each with a guard condition. Only one alternative can be true.
  • critical - a fragment within a larger parallel Interaction Frame that when entered suspends the interleaving of events from the other fragments.
  • loop - the fragment iterates according to a guard condition.
  • neg - an invalid interaction.
  • opt - single alternative with a guard condition.
  • par - each fragment is run in parallel.
  • ref - an interaction defined in another diagram.
  • strict - a fragment with the ordering of reception events across multiple lifelines follow strictly their graphical arrangement.