A Guide to UML Collaboration Diagram

Read this article to learn about the definition, symbols, examples, and use cases of collaboration diagram and how to make them.


In software engineering, UML collaboration diagrams visualize how system objects interact, highlighting relationships and communications. They help pinpoint issues early, crucial for building robust software.

In this article, we will delve into what collaboration diagrams are, their key components, and how they can be used to enhance system design and communication within development teams.

In this article
  1. What is a Collaboration Diagram?
  2. How to Draw a Collaboration Diagram?
  3. 3 Collaboration Diagram Examples
  4. Conclusion

Part 1. What is a Collaboration Diagram?

A Collaboration Diagram, also known as a Communication Diagram in UML (Unified Modeling Language), is a visualization tool used to illustrate the interactions between objects in a system. It focuses on how objects collaborate to achieve a specific behavior or to complete a process.

Due to the uniqueness of these collaboration diagrams, they are used for analysis purposes. You would be able to understand even the smallest interactions between the objects in the diagram. When there are a lot of objects to show in a diagram, it gets difficult to present them in a main diagram. So, a collaboration diagram is used in such scenarios to better understand the objects working together.

Collaboration Diagram Symbols

The symbols and notations for collaboration diagrams are of great value. There are numbers used for specific actions or interactions in these diagrams, making it important to know about the collaboration diagram. The following four main elements and their important notations are used in the collaboration diagram.


An actor is considered the main element of the collaboration diagram. An actor is the one from where the interaction starts and is the starting point of the diagram. There could be more than one actor in the system, so they are named differently.

how to denote collaboration diagram


The second most important element of the diagram is an object, and there could be many objects in one model depending on the complexity of the system. They are denoted as follows; "Object Name: Class Name". Class Name is important to mention when you mention an object in the diagram. However, if there is more than one object in a single class, you don't need to mention the class name for those objects.

how to represent the object in a collaboration diagram


Solid lines denote links in the collaboration diagram. These are the connections between the actors and the objects in the diagram. It is a route that tells you the message will be delivered from one object to the other.



A Message is the fourth element of the collaboration diagram. It is denoted by the arrowhead line and directed towards the receiver object. It is usually shown above or below the link line having a number.

how to represent messages in a collaboration diagram

When do We Use a Collaboration Diagram?

The roles of the sequence diagram and collaboration diagram are approximately the same. However, a collaboration diagram is used when it is crucial to understand the relations between the objects in the system. They are best suited for analysis of the use cases.

They are best used while modeling architectural design. The mechanism is best understood through these diagrams.

The role of each object is defined in these diagrams, and functionality from one object to the other is recorded through messages for better results.

The messages in these diagrams are numbered as 1,2,3, and so on. For instance, the top-level message is written as 1, and the same call message is denoted by the same number but in the form of a prefix having different suffixes.

So, there is a unique purpose of these diagrams for more clarity. The software engineers pick it up early and understand a complex system within minutes.

Part 2. How to Draw a Collaboration Diagram?

Creating a collaboration diagram is not as hard as you think. Follow the simple steps below:

Step 1: Identify the model and what you need for the system.

Step 2: Start creating the diagram with an actor. If there are multiple actors in the diagram, show them separately.

Step 3: Identify the objects in your model. Each object has separate roles, so arrange them in the correct sequence. The flow of the diagram is crucial to run the model correctly. You might see errors while executing if the flow isn't right.

Step 4: Link your objects to run the model correctly and write messages according to the needs of your model.

Step 5: Write messages with clear instructions and draw an arrowhead in the direction of the next object.

These were a few of the steps to follow and make a simple collaboration diagram. The diagram should be visually correct and provide enough information to understand model attributes.

Part 3. Collaboration Diagram Examples

Here are a few examples of the collaboration diagrams.

Admin Panel Collaboration Diagram

In this collaboration diagram for the admin system, the elements of the system are well described. The messages and links for all the elements are separately written in the model. The actor or the user's identity logs into the system through a password. The admin portal is opened for other actions when the entered password is accepted. Other objects for the system include adding products, subcategories, profile management, etc. Then, the user is allowed to log out of the system.

how to draw admin panel collaboration diagram

Collaboration Diagram for Phone Call Mechanism

Another simple example of the collaboration diagram is the phone call mechanism. When someone calls another person, this call has to pass through a few processes. A caller dials the number and passes the message to the exchange (object). The ringtone rings at the other end of the receiver's cell phone. The receiver receives the call and talks. Otherwise, it ends automatically. This collaboration diagram has the four objects only. There could be more for complex systems as well.

collaboration diagram for phone call mechanism

Collaboration Diagram for Ticket Processing System

Online ticket booking is explained in this collaboration diagram. A user or the actor opens the ticket system where he finds the available booking. If the tickets are not available, the system rejects the actions. When it is available, it proceeds to book the tickets. Most of the ticket booking systems work on this pattern. There are a few of the systems where feedback is given; it all depends on the users if they want to make a statement about that or not.

how to design collaboration diagram for ticket system


UML collaboration diagrams are of greater importance. They are necessary for multiple purposes, starting from understanding to execution. As a software engineer, you must execute things correctly and represent your model before the business owners to let them know how it would work.

However, it could get itchy to start creating those diagrams if you don't have the right tools. For this, a template could help you easily get your work done. So, all you need is a kickstart and the right tools to create a collaboration diagram.

There are multiple templates available to create online collaboration diagrams. These templates have all the elements to work with, making it easier to complete your model within minutes. Edrawmax is one of those, providing help in making these models. Try now and fill your model with color to make it stand out.

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Edraw Team
Edraw Team Jul 04, 24
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