at one end of an Association to retrieve Objects from the other end. Associations need not be navigable. Node - Note - It is an explanatory part of UML models. A note is a symbol for rendering constraints and comments attached to an element or collection of elements. 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. P Package - A package is a collection or grouping of related classes or of classes with related functionality. Package diagram Parameter - data passed in a Message to be used within the Method Partition - section of an Activity diagram or Sequence diagram occupied by a single Class or Object Pin - a parameter of an Action Polymorphism - the ability of Objects belonging to different Classes to respond to Operations of the same name, each one according to the right Class-specific behaviour Profile - Provides a generic extension mechanism for building UML models. Other extension mechanisms include stereotypes. Property - an Attribute or an Association Property-string - a qualifier for Attributes and Operations. Examples include {ordered}, {readonly}, {unique}. Q Qualified association - tightens the multiplicity or role of an association between 2 classes by dividing the set of objects into subsets based on a value of the qualifier—an attribute of the