A sequence diagram, also known as an event diagram is a type of UML diagram that shows a sequence of events and interaction of objects in a time sequence. At a glance, you will see different objects along a vertical axis which represents the time messages are carried out. There is also a horizontal axis that illustrates the objects or elements involved in the system. This is primarily used to understand the requirements of a system and document the operation’s process. They are helpful for operations like hotel reservations or enrollment systems. But in order to create this diagram, you need a sequence diagram tool like the ones we will discuss below.
A Diagram Gate is a simple graphical way to indicate the point at which messages can be transmitted into and out of interaction fragments. Diagram Gate The State/Continuation element serves two different purposes for Sequence diagrams, as State Invariants and Continuations.
Top Free Sequence Diagram Tools
SequenceDiagram.org is an online tool / software for creating UML sequence diagrams. Founded in 2014 with the purpose to improve the efficiency when creating and working with sequence diagrams by combining text notation scripting and drawing by clicking and dragging in the same model. All parsing, processing, and drawing is done client side. Sequence diagrams are the most popular UML artifact for dynamic modeling, which focuses on identifying the behavior within your system. The sequence diagram is a construct of a message sequence chart. A sequence diagram shows object interactions arranged in time sequence. It depicts the objects and classes involved in the scenario and the.
Score: 4.8 / 5
GitMind comes with a large library of templates and themes allowing you to produce and streamline your diagrams. It helps you create visually pleasing sequence diagrams with its easy-to-use interface. Also, it has a lot of shapes for better diagramming and generates different types of diagrams. Furthermore, it allows you to share projects and collaborate with other team members.
Score: 4.6 / 5
Pricing: Free, $7.95 for a starter plan
A sequence diagram can also be made with Lucidchart. Users can draw various visual illustrations, from simple to technical diagrams. And like GitMind, this sequence diagram tool can improve the creation process with its collaboration feature. In addition to that, it has a sequence markup feature in which you only need to type the order and rules of the system. By then, the diagram will be automatically generated showing the objects and operations involved in the process.
Score: 4.2 / 5
Pricing: Free; $5 monthly
Visual Paradigm is another free diagramming tool that can help you draw professional diagrams. The sequence diagram tool does not limit the number of diagrams or shapes, there are no ads, and you can enjoy the tool for as long as you’d like.
Score: 3.9 / 5
Create your own sequence diagram using a professional sequence diagramming tool called StarUML. This program was developed specifically to create UML diagrams like sequence diagrams. It offers standardized UML shapes including arrows and labels. For those who are coding a system, you can also import your program’s code and display it as a diagram.
Score: 3.8 / 5
Pricing: Free; $4.99
Looking for a free online sequence diagram generator? Gliffy is the right program for you. With this tool, you will be able to create diagrams anywhere. It also fully integrates with the Atlassian products Confluence and Jira. This means you can continue creating previously made diagrams without leaving the Atlassian environment, thereby increasing the team’s productivity.
Score: 3.8 / 5
Pricing: Free; $4.95 monthly
Creately offers ready-made sequence diagram templates to help you easily create a sequence diagram for your business or organization. This sequence diagram generator lets you pick a suitable template to match the common processes or scenarios. It also supports other types of UML diagrams like Use case, DFD, and ER.
Score: 3.5 / 5
How To Create Sequence Diagrams
UMLetino 14.3 is another free online UML tool and you don’t need to install any plugins. Unlike other tools though, the program isn’t visually appealing. The interface, shape selection tools, and customization options are very simple but still enough to create a comprehensive sequence diagram. At the same time, this sequence diagram maker gives you the capability to import and export from and to Dropbox.
Simple Sequence Diagram Generator
Like any other diagram, a sequence diagram makes it easy to understand the processes or operation of a system. Thus, if you want to model a sequence diagram of your business or understand the requirements of a system, then these free online sequence tools can get the job done. They are easy-to-use and anyone can use them, with just the basic knowledge of a sequence diagram.
Creating a Sequence Diagram from a Class
- Download Simple-Registration.vpp. You can also find this file at the bottom of this tutorial.
- Open the downloaded .vpp file in Visual Paradigm. To open a project, select Project > Open from the application toolbar.
- Open the class diagram Registration. Study the diagram content. We have three classes - RegistrationUI, RegistrationController and User.
- Now, we want to model the interaction between object instances of these classes in runtime. Since the controller class is responsible to control the registration process, add a sub-sequence diagram from it. Move the mouse pointer to RegistrationController. Click on the resource icon at the bottom right corner and select New Diagram... from the popup menu.
- In the New Diagram window, select Sequence Diagram and click Next. Keep the diagram name as provided and click OK to confirm. This creates an empty UML sequence diagram.
Drawing the Sequence Diagram
- Select Boundary Lifeline (B) from the diagram toolbar.
- Click on the diagram to create a boundary lifeline.
- Enter registrationUI as the name of lifelife and then press Enter to confirm.
- Right-click on the lifeline and select Select Class > Select Class... from the popup menu.
- In the Select Class window, select the RegistrationUI class and then click OK to confirm.
After that, the lifeline will look like the following.
- Create a Control LifelineregistrationController : RegistrationController and an Entity Lifelineuser : User. Don't forget to select the appropriate classes for them. The diagram will look like the following.
- Let's model the method invocations between lifelines. Move the mouse pointer over lifeline registrationUI.
- Press on the Resource Catalog resource and drag it out.
- Move to lifeline registrationController and release the mouse button.
- Select Message from Resource Catalog.
- This pops up a list of name that you can choose for the new sequence message. You can see that those are operation of classRegistrationController. Select createUser(name, password).
- Relate lifeline registrationController and user. We say that registrationController creates the user lifeline. Therefore, we need to relate them with a create message. Move the mouse pointer over the activation in lifeline registrationController.
- Press on the resource Resource Catalog and drag it out.
- Release the mouse button on the lifeline user.
- Select Create Message from Resource Catalog.
Create message is created. Your diagram should look like this:
- Create messages setName and setPassword from lifeline registrationController to user. Up to now, the diagram becomes:
- You can also specify the arguments of operations. Take the message createUser(name, password) as example. Right-click on it and select Open Specification... from the popup menu.
- Edit the action type property by clicking on the button with dotted caption, next to Action type.
- In the Call Action Specification window, click Add > Text... to add an argument. In this example, click Add > Text... to add argument peter. Click Add > Text... again to add argument mypwd. Note that the two arguments are actually referring to the two parameters given by the operation. If you add the third argument here, it will be ignored (as there are only two operations defined).
- Click OK to close the windows and go back to diagram. The arguments are added and presented on diagram. Finally the diagram become: