State Diagram Explained

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What Is A State Diagram in UML?

A UML state diagram is a behavioral diagram used to represent a system's conditions at a given time. It shows the changes in the system in response to factors such as time and other events.

Why Use A State Diagram?

A state can be defined as a set of values that define an object, which is grouped together based on characteristics that can affect an object or system's overall behavior. State diagrams are used to depict the states and the transitions between states. Other uses for state diagrams include:

  • Modeling the dynamic aspects of a system’s behavior
  • Depicting how objects transition between various states during its lifetime
  • Exploring how and why certain external and internal factors can cause objects to react in a particular way

State Diagram Symbols

Here is a list of commonly used symbols and notations when drawing a UML state diagram.

state diagram uml initial Initial

A solid black circle symbolizes the initial state of the system.

state diagram uml state State

A state is represented by a rounded rectangle.

transition Transition

An arrow - labeled with the event that causes a state change - between two states represents a transition.

fork Fork

A fork symbolizes a state being split into two or more concurrent states.

join Join

A join symbolizes two concurrent states converging into one.

self transition Self transition

When an object's state doesn't change upon an event's occurrence, this is known as a self transition.

composite state Composite State

A state with internal activities occurring on the inside is known as composite states.

final Fork


How to Draw A State Diagram in EdrawMax?

EdrawMax’s intuitive software allows you to create your own state diagrams. Whether it’s a basic or complex one, follow this outline to create one that fits your needs.

  • Step 1: In your browser, visit https://www.edrawmax.com/online/ to access the online version, or download the desktop version at https://www.edrawsoft.com/download-edrawmax.html
  • Step 2: In the white sidebar, click on Software Development. Then, click on the UML Modelling box that appears near the top of the screen.
  • use case diagram edrawmax window 1
  • Step 3: Choose a template, or click on the UML Modelling box with the “ + ” to open a new document.
  • use case diagram uml
  • Step 4: The symbol library can be found to the left of the screen. Scroll down further to find more UML-related symbols. Once you’ve selected the symbols you need, click ‘OK’ and add the shapes to the toolbar on the left.
  • use case diagram edrawmax
  • Step 5: Simply drag the components you need from the symbol library onto the blank document to start creating. Each element can be moved, resized, or customized to fit your needs.

State Diagram Examples

Diagram 1: State diagram - checking calendar availability

This is an example of chekcing calendar availability.

checking calendar availability

Diagram 2: State diagram - processing an airline passenger

This is an example about the process of airline passenger.

processing an airline passenger

Summary

UML state diagrams are a useful tool for software developers and business users alike to map out a system's behavior. Be sure to try out EdrawMax, making drawing diagrams such as these so simple and intuitive.