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Glossary Page



  1. An atomic constituent of a model.
  2. A model object of any type, such as Class, Component, Node or Object.


Used in Interaction diagrams to reflect a lost message in sequence.


A store or persistence mechanism that captures the information or knowledge in a system. It is the Model in the Model-View-Controller pattern.

entry action

An action executed upon entering a state in a State Machine regardless of the transition taken to reach that state.

entry point

Used to define where external states can enter a Sub Machine.


A list of named values used as the range of a particular attribute type. For example, RGBColor = {red, green, blue}. Boolean is a predefined enumeration with values from the set {false, true}.


The specification of a significant occurrence that has a location in time and space. In the context of State diagrams, an event is an occurrence that can trigger a transition.

exception handler

An element that defines the group of operations to carry out when an exception occurs.

exit action

An action executed upon exiting a State in a State Machine regardless of the transition taken to exit that State.

exit point

Used in Sub Machine states and State Machines to denote the point where the machine is exited and the transition sourcing this exit point, for Sub Machines, is triggered. Exit points are a type of pseudo-state used in the State Machine diagram.


In the context of packages, to make an element visible outside its enclosing namespace.

See also: visibility

Contrast: import

expose interface

A toolbox icon that is a graphical way to depict the required and supplied interfaces of a Component, Class or Part.


A string that evaluates to a value of a particular type. For example, the expression (7 + 5 * 3) evaluates to a value of type number. A relationship from an extension Use Case to a base Use Case, specifying how the behavior defined for the extension Use Case augments (subject to conditions specified in the extension) the behavior defined for the base Use Case. The behavior is inserted at the location defined by the extension point in the base Use Case. The base Use Case does not depend on performing the behavior of the extension Use Case.

See also: extend, include


A connector used to indicate that an element extends the behavior of another. Extensions are used in Use Case models to indicate one Use Case (optionally) extends the behavior of another.

See also: expression, include