A Brief UML Glossary

Activity: A step or action within an Activity Diagram. Represents an action taken by the system or by an Actor.

Activity Diagram: A glorified flowchart that shows the steps and decisions and parallel operations within a process, such as an algorithm or a business process.

Actor: A person or external computer system that interacts with the system under design.

Association: A connection between two elements of a Model. This might represent a member variable in code, or the association between a personnel record and the person it represents, or a relation between two categories of workers, or any similar relationship. By default, both elements in an Association are equal, and are aware of each other through the Association. An Association can also be a Navigable Association, meaning that the source end of the association is aware of the target end, but not vice versa.

Association Class: A Class that represents and adds information to the Association between two other Classes.

Attribute: A data field or property that represents information about a Classifier.

Base Class: A Class which defines Attributes and Operations that are inherited by a Subclass via a Generalization relationship.

Branch: A decision point in an Activity Diagram. Multiple Transitions emerge from the Branch, each with a Guard Condition. When control reaches the Branch, exactly one Guard Condition must be true; and control follows the corresponding Transition.

Class: A category of similar Objects, all described by the same Attributes and Operations and all assignment-compatible.

Class Diagram: A diagram that shows relationships between various Classes and Interfaces.

Classifier: A UML element that has Attributes and Operations. Specifically, Actors, Classes, and Interfaces.

Collaboration: A relation between two Objects in a Collaboration Diagram, indicating that Messages can pass back and forth between the Objects.

Collaboration Diagram: A diagram that shows Collaborations between Objects and the Messages that pass along those Collaborations to carry out some behavior.

Component: A deployable unit of code within the system.

Component Diagram: A diagram that shows relations between various Components and Interfaces.

Dependence: A relationship that indicates one Classifier knows the Attributes and Operations of another Classifier, but isn't directly connected to any instance of the second Classifier.

Deployment Diagram: A diagram that shows relations between various Processors.

Element: Any item that appears in a Model.

Event: In a State Diagram, this represents a signal or event or input that causes the system to take an action or switch States.

Final State: In a State Diagram or an Activity Diagram, this indicates a point at which the diagram completes.

Fork: A point in an Activity Diagram where multiple parallel control threads begin.

Generalization: An inheritance relationship, in which a Subclass inherits and adds to the Attributes and Operations of a Base Class.

Initial State: In a State Diagram or an Activity Diagram, this indicates the point at which the diagram begins.

Interface: A Classifier that defines Attributes and Operations that form a contract for behavior. A provider Class or Component may elect to Realize an Interface (i.e., implement its Attributes and Operations). A client Class or Component may then Depend upon the Interface and thus use the provider without any details of the true Class of the provider.

Join: A point in an Activity Diagram where multiple parallel control threads synchronize and rejoin.

Lifeline: A line in a Sequence Diagram that indicates the duration of an Object.

Member: An Attribute or an Operation within a Classifier.

Merge: A point in an Activity Diagram where different control paths come together.

Message: In a Sequence Diagram or a Collaboration Diagram, a communication from one Object to another, deliverung information or requesting a service.

Model: The central UML artifact. Consists of various elements arranged in a hierarchy by Packages, with relations between elements as well.

Navigability: Indicates which end of a relationship is aware of the other end. Relationships can have bidirectional Navigability (each end is aware of the other) or single directional Navigability (one end is aware of the other, but not vice versa).

Navigable Association: An Association with single directional Navigability.

Note: A text note added to a diagram to explain the diagram in more detail.

Note Attachment: A dashed line connecting a Note to an element that it describes.

Object: In an Activity Diagram, an object that receives information from Activities or provides information to Activities. In a Collaboartion Diagram or a Sequence Diagram, an object that participates in the scenario depicted in the diagram. In general: one instance or example of a given Classifier (Actor, Class, or Interface).

Operation: A method or function that a Classifier can perform.

Package: A Model element that divides the Model into a hierarchy.

Package Diagram: A Class Diagram in which all of the elements are Packages and Dependencies.

Parameter: An argument to an Operation.

Private: A Visibility level applied to an Attribute or an Operation, indicating that only code for the Classifier that contains the member can access the member.

Processor: In a Deployment Diagram, this represents a computer or other programmable device where code may be deployed.

Protected: A Visibility level applied to an Attribute or an Operation, indicating that only code for the Classifier that contains the member or for its Subclasses can access the member.

Public: A Visibility level applied to an Attribute or an Operation, indicating that any code can access the member.

Realization: Indicates that a Component or a Class provides a given Interface.

Sequence Diagram: A diagram that shows the existence of Objects over time, and the Messages that pass between those Objects over time to carry out some behavior.

State: In a State Diagram, this represents one state of a system or subsystem: what it is doing at a point in time, as well as the values of its data.

State Diagram: A diagram that shows States of a system or subsystem, Transitions between States, and the Events that cause the Transitions.

Static: A modifier to an Attribute to indicate that there's only one copy of the Attribute shared among all instances of the Classifier. A modifier to an Operation to indicate that the Operation stands on its own and doesn't operate on one specific instance of the Classifier.

Stereotype: A modifier applied to a Model element indicating something about it which can't normally be expressed in UML. In essence, Stereotypes allow you to define your own "dialect" of UML.

Subclass: A Class which inherits Attributes and Operations that are defined by a Subclass via a Generalization relationship.

Swimlane: An element of an Activity Diagram that indicates what parts of a system or a domain perform particular Activities. All Activities within a Swimlane are the responsibility of the Object, Component, or Actor represented by the Swimlane.

Transition: In an Activity Diagram, represents a flow of control from one Activity or Branch or Merge or Fork or Join to another. In a State Diagram, represents a change from one State to another.

Use Case: In a Use Case Diagram, represents an action that the system takes in response to some request from an Actor.

Use Case Diagram: A diagram that shows relations between Actors and Use Cases.

Visibility: A modifier to an Attribute or Operation that indicates what code has access to the member. Visibility levels include Public, Protected, and Private.

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