Use Case Diagram

What is the Use Case Diagram? Examples.


Use Case Diagram


Use case diagram:

A use case diagram is a graphical representation of interactions. This interaction is among the elements of a system. A use case is a methodology. It is used in the system analysis. Its purpose is to identify, clarify, and organize system requirements.

Where the term “system” refers to something being developed or operated. These diagrams are engaged in UML. UML stands for Unified Modeling Language. It is a standard notation for modeling real-world objects and systems. The objectives of a system can include the following:

  • Planning overall requirements
  • Validating a hardware design
  • Testing a software product under development
  • Debugging a software product under development
  • Creating an online help reference
  • Performing a consumer service-oriented task

The Basic purpose of use case diagram

The purpose of the usecase diagram is to demonstrate different ways. Using these ways the user can interact with the system.



Here is a simple example of usecase diagram of “PRODUCT SALES ENVIRONMENT” / “RESTAURANT MANAGEMENT”.

This example will include the following:

  • Item ordering
  • Catalog updating
  • Payment processing
  • Customer relations

A usecase diagram will contain four components given below.

  1. The boundary: It will define the system of interest in relation to the world.
  2. The actors: It will define the individuals according to their roles.
  3. The use case: It will define the specific roles played by actors within and around the system.
  4. The relationships: It will define the relationships among actors and use cases.


A use case diagram looks like a flowchart. Instinctive symbols are used to represent the system elements. The graphical representation of the use case diagram of “RESTAURANT MANAGEMENT” is as under.


Use Case Diagram


Basic  Usecase diagram symbols 


A rectangle symbol represents the boundary. It is a system’s boundary. We place an actor outside the system’s boundary.

Use case:

Ovals represent use cases. We label ovals with verbs to represent the system’s function.


These are the users of the system. If one system is the actor in another system. We label the actor system with the actor stereotype.


A simple line illustrates the relationship between an actor and the use case. Arrows labeled as “uses” or “extends” are used for relationships among the use cases. Where “uses” indicates that one use case needs another to perform the task. And “extends” indicates alternative options.


Use Case Diagram symbols

Read more: What is UML

Why make use case diagram

Use case diagrams are valuable. They are used to visualize the functional requirements of a system. This visualization is translated into design choices and development priorities.

They are helpful in identifying internal and external factors. The factors that may influence the system. Such factors should be taken into consideration.

They also provide a high level of analysis from outside the system.


Ideal conditions to use these diagrams:

  • To represent the goals of system-user interactions
  • To define and organize the functional requirements in a system
  • To specify the context and requirements of a system
  • To model the basic flow of events in a use case


Advantages of UML use case diagrams

  • It is easy to write.
  • It is easy to understand.
  • It is easy to use.
  • It is written in the users’ language.
  • It provides easy scenarios that are understood by both sides.
  • It links the design and implementation activities.
  • It helps to visualize the complex system.
  • Its scenarios can be used for validation.
  • It engages the users in the requirement process.


Disadvantages of UML use case diagrams

  • It takes a lot of time to keep the diagram reasonable.
  • It takes time to synchronize with the actual code.
  • It cannot represent every condition in a sequence.
  • Good UML software is always costly.
  • It takes some time to master it properly.

Read more:

State Diagram