Common Mechanisms of UML

UML Diagrams 

Introduction to the UML Diagrams

• They are graphical representations of the model 
• They are connected graphs of vertices (things) connected by links (relationships) 
• Diagrams are drawn to visualize a system from different perspectives 
• An element in the system may appear in multiple diagrams 

The UML diagrams are mainly classified as: 

1. Class Diagram 
2. Object Diagram 
3. Use Case Diagram
4. Sequence Diagram
5. Collaboration Diagram
6. Statechart Diagram
7. Activity Diagram 
8. Component Diagram 
9. Deployment Diagram

Structural diagrams representing static aspects of a system 

Behavioral diagrams representing dynamic aspects of a system 

 

Class Diagram: 

• It is the most common diagram found in object-oriented analysis and design
• It shows set of classes, interfaces, collaborations and their relationships 
• Models the static view of the system 
• Object Oriented Design(OOAD) has two types of diagrams, static and dynamic 
• Static diagrams are represented as Class diagrams, while Dynamic diagrams are represented as State, Sequence and/or Collaboration diagrams

Object Diagram: 

• A snapshot of a class diagram 
• Models the instances of things contained in a class diagram 

Use Case Diagram: 

• Models WHAT the system is expected to do 
• Shows a set of Use Cases (sets of functionality performed by the system), the actors and their relationships 
• Use Case diagrams model the behavior of a system, a subsystem or a class 
• Use Case diagrams are important for visualizing, specifying and documenting behavior of an element 

Sequence Diagram: 

• Sequence Diagrams are a kind of object interaction diagrams 
• Sequence Diagram models the flow of messages by time-ordering 

Collaboration Diagram: 

• It is a another kind of object interaction diagrams 
• Merely depicts the messages passed between objects 

Statechart Diagram: 

• Statechart diagram shows a state machine that consist of states, transitions, events and activities 
• They are important in modeling the behavior of an interface, class or collaboration 

Activity Diagram:  

• It shows the flow of activity from one activity to another within a system 
• Important in modeling the functions of a system 

Component Diagram: 

• It shows the physical packaging of a system in terms of components and dependencies between them 

Deployment Diagram: 

• It shows the configuration of the processing nodes at runtime and the components that live on them