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Glossary Page


abstract class

A Class that cannot be directly instantiated.

Contrast: concrete class


The essential characteristics of an entity that distinguish it from all other kinds of entities. An abstraction defines a boundary relative to the perspective of the viewer.


The specification of an executable statement that forms an abstraction of a computation procedure. An action typically results in a change in the state of the system, and can be realized by sending a message to an object or modifying a connector or a value of an attribute.

action sequence

An expression that resolves to a sequence of actions.

action state

A state that represents the execution of an atomic action, typically the invocation of an operation.


The execution of an action.

active class

A Class whose instances are active objects. When instantiated, an active Class controls its execution. Rather than being invoked or activated by other objects, it can operate standalone, and define its own thread of behavior.

See also: active object

active object

An object that owns a thread and can initiate control activity. An instance of active Class.

See also: active class, thread


Defines the bounds for the structural organization that contains a set of basic or fundamental behaviors. It can used to model procedural type application development for system design through to modeling business processes in organizational structures and work flow.

activity diagram

A diagram used to model procedural type application development for system design through to modeling business processes in organizational structures and work flow.

activity graph

A special case of a State Machine that is used to model processes involving one or more classifiers.

Contrast: state chart diagram

actor [class]

A coherent set of roles that users of Use Cases play when interacting with these Use Cases. An Actor has one role for each Use Case with which it communicates.

actual parameter

A binding for a parameter that resolves to a run-time instance.

Synonym: argument

Contrast: (formal) parameter

aggregate [class]

A Class that represents the 'whole' in an Aggregation (whole-part) relationship.

See also: aggregation


A special form of Association that specifies a whole-part relationship between the Aggregate (whole) and a component part.

See also: composition


The part of the software development process whose primary purpose is to formulate a model of the problem domain. Analysis focuses on what to do, design focuses on how to do it.

Contrast: design

analysis diagram

A diagram used to capture high level business processes and early models of system behavior and elements. It is less formal than some other diagrams, but provides a good means of capturing the essential business characteristics and requirements.

analysis time

Refers to something that occurs during an analysis phase of the software development process.

See also: modeling time, run time, compile time

Contrast: design time


The organizational structure and associated behavior of a system. An architecture can be recursively decomposed into parts that interact through interfaces, relationships that connect parts, and constraints for assembling parts. Parts that interact through interfaces include Classes, Components and subsystems.


A binding for a parameter that resolves to a run-time instance.

Synonym: actual parameter

Contrast: (formal) parameter


A physical piece of information that is used or produced by a business or development process. Examples of Artifacts include models, source files, scripts, and binary executable files. An Artifact can constitute the implementation of a deployable component.

Synonym: product

Contrast: component


A connector that bridges the required interface of a component with the provided interface of a second component.


The semantic relationship between two or more classifiers that specifies connections among their instances.

See also: link

association class

A model element that has both Association and Class properties. An Association Class can be seen as an Association that also has Class properties, or as a Class that also has Association properties.

See also: class

association end

The endpoint of an Association, which connects the Association to a classifier.

See also: classifier, link end


A feature within a classifier that describes a range of values that instances of the classifier can hold.

auxiliary class

A stereotyped Class that supports another more central or fundamental Class, typically by implementing secondary logic or control flow. Auxiliary Classes are typically used together with focus Classes, and are particularly useful for specifying the secondary business logic or control flow of components during design.

See also: focus class