Common Mechanisms of UML

Structural Things
Structural Things are the conceptual or physical elements of the system. They are normally identified through noun identification.

• Class
• Interface
• Use Case
• Collaboration
• Active Class
• Component
• Node

Class
Describes a set of objects that share same attributes, operations, relationships and semantics
It is represented as rectangle with three compartments.

Interface
It is a collection of operations that specify the services of a class or component and is represented by a circle
A class uses interfaces that are implemented by other classes
Semi circle shows an interface required by a class form some other class

Use Case
It is used to describe the list of steps to be performed by a system to achieve a goal
A use case is realized by collaboration
It is represented as ellipse with solid line

Collaboration
A collection of UML building blocks (classes, interfaces, relationships) that work together to provide some functionality within the system
Collaborations have structural and behavioral dimensions
In structural part, these are the classes, interfaces and other elements that work together to carry out the functionalities
In behavioral part, dynamics of those elements that interact are specified
It is represented as an ellipse with dashed lines

Active Class
A class whose instance is an active object
An active object has processes or threads (units of execution)
It is represented like a class with double lines on the left and right

Component
It is a modular part of a system that can be replaced with a part of similar logical behavior
It is represented as a rectangle with tabs

Node
It is a physical element that exists at runtime and represents a computational resource, that have atleast some memory and processing capability
It is represented as a cube