UML Diagram Types | UML Guide & Useful Tutorials

By Marin Valchev On Apr 4, 2016

UML diagrams can be a really powerful tool. But UML (Unified Modeling Language) is very detailed and sophisticated. So the purpose of this article is to provide you with a simple guide to UML diagram types, how to use them in business and IT, tutorials, examples, and tips.

I will pay most attention to activity, sequence, state, use case UML diagrams because they can be made fast and can be used in day-to-day business tasks.

Table of Contents

What is UML?

At first, UML or Unified Modelling Language is used in software development for a visual representation of systems, their design, integration, etc. But it does not mean that this “language” is for ITs only.

For me as personal opinion UML is a standard which defines how to create useful diagrams, what are their elements, connections, etc.

What is the main problem? UML is sophisticated. It needs time to create a diagram and it needs time to understand it.

So this article will provide you with information how to create and use most important UML diagram types in a fast and simple way. And not only in the IT, but in any area of business.

UML diagram types

There are two major UML diagram types – Structure and Behavior.

Obviously, when it comes to business behavior diagrams are way more important. We can represent customer “behavior”, procedure steps, communications, entity relations, and etc useful things.

The most important diagrams are activity, state, use case, sequence and they will be explained below in this article.

The structure diagrams (class, component, object) are more IT and engineering oriented. OK, we can use the for creating organization structure. But they are more “techie”. I will provide some info for them in “Other UML diagram”.

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Activity Diagram

Maybe the most business oriented UML diagram. Because it represents processes as workflows with steps and actions. And doing business is a process. I mean a customer phone to call center goes is a process with steps, right?

Here is a very simple example of activity diagram:

Even in this simple example, you can see how powerful is the activity diagram when you need to define a process.

It can be used away outside pure IT. Any procedure, process, interaction, workflows can be represented by activity diagrams.

The elements are quite simple:

Start/End notations
Swimlanes which define responsibility
Activity – steps with some basic information
Decisions – Yes/NO
Connectors which represent the flow
Some text, notes, etc

Of course, you can have much more notations – forks, systems, databases, document, predefined process, etc.

But the core about activity diagram are not the notation but is meaning. It is a step-by-step process and it is applicable in any business area – trade, finance, IT, customer service, logistic, etc.

Activity Diagrams are extremely important when you have long documentation. Having 2-3 diagrams shared to experts which are not 100 % involved in some business activity instead of 300 hundred page document is quite useful.

If you need more information about UML you can check on www.uml.org.

If you need software tools in order to make nice activity diagrams, you can check on my page business process management software.
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Use Case Diagram

Use Case Diagram is one of the most important and useful UML tools you can have.

It is fast for drawing and has some simple elements /see the example/. Most basic of them are:

Actors
Use Cases
Link between them
Extend/Include
Scope

Why is this diagram useful?

First, it set boundaries. You can clearly see which use cases are in the scope of a project, contract, etc. If some use case is out of scope you can set it outside from the scope for more clarity.

Second, it shows high-level connections. You can see who is doing what.

Third, you can have additional extend / include relations in order to provide connections between use cases. For example – the use case Manage Agents can be extended to Manage Superagents.

Fourth, most important – it provides a great high-level view. You have a meeting with C – Level management. Excellent! Prepare this diagram, it will help. You can show them sophisticated activity diagrams. They are busy you know.

Because of all the above reasons UML Use Case diagrams is an excellent addition to any high-level negotiations, contracts, project scope definition, etc. Of course, IT projects benefits most of it because it defines system boundaries, but all other business activities can benefit from Use Case diagram boundaries and clarity.
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Sequence diagram

Sequence diagram is one of most popular UML diagram types.

But frankly speaking, it is used mostly by ITs and engineers. Why? Because sequence diagrams allow you to display communication between different systems.

But you can use it from a business perspective also.

First, if you have IT project or you deal with many systems make sure that there are at least one sequence diagram. Share it with all ITs and engineers. Such diagram confirms that you have at least one technical expert who has a deep understanding of the systems. And all other technical experts are informed and agree.

Second, you can use sequence diagrams to visualize communication between different departments, sectors, etc. From this point of a view, sequence diagram looks like UML activity diagram. But there are differences – activity diagram is better if you have workflows, steps, exceptions, etc. But if you need to focus on communication – triggers, types, directions, results – then sequence diagram could be better.

State Machine Diagram (Status Diagram)

State Machine diagram (known as Status Diagram also) is one of the most sophisticated UML diagram types.

It is very useful in the technical world. Of course, if ITs or engineers have enough time.

But full scale of state machine diagram is unusable in a business world.

From the other hand, a simplified status diagram can be a powerful tool.

What does have one state machine diagram – all statuses of one entity, connection between them and (optional) responsible person.

When do I use it? If I have an entity with three and more statuses I always draw such diagram in a simplified way. You can see the state machine diagram example above.

It is simple, right? But it provides to customers, managers, ITs very consistent information. All account statuses, all mapping between them and all responsible experts.

If you share such simple diagram nobody will claim that he/she does not know or did not understand.
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Other UML diagrams

Let me share some information for other UML diagram types. Mostly structure ones.

Frankly speaking, I do not use them in my day-to-day work. One exception – sometimes I use them for organization charts.

In any case, structure UML diagrams are applicable mostly for developers, system admins, engineers, and etc. If you are dealing with such experts, just be careful and request some diagrams from them.

Class diagram – this diagram visualize classes, their attributes, methods, and the relationships among them.

As you see from the example, it is mostly for developers and other ITs.

So if you have some software project it would be a good idea to request such diagrams together with other documentation.

Component Diagram – one of most sophisticated UML diagrams. Totally technical, mostly for engineers. It represents components include executables, documents, database tables, files, and library files as stereotypes with connectors between them.

Composite Structure Diagram – It represents internal structure of an entity and the connections with other structures. Usually used for data so it is mostly software diagram. Composite Structure diagram contains parts, ports, connectors, classifiers.

Deployment Diagram – it represents the deployment of network or software. The deployment diagram has all hardware components (nodes), software components (artifacts) and connections between them. Obviously, this diagram is applicable for software engineers, system administrators, and support expert. From a business perspective – it is a nice addition to deployment or GO-Live plans.

Object Diagram – closely related to class diagrams but object diagrams usually have specific values for its attributes. We can consider class diagram as more abstact while object diagram is more.

There are even more UML diagram types as Package diagrams, Composite diagrams, Profile diagrams and etc. Their usage is limited from a business perspective but they are useful for ITs and engineers.

If you need more detailed information, you can check Wiki or uml.org.
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UML Software Tools

There are numbers of great software for UML diagrams. For example, the diagrams in this article are made via draw.io – free online diagramming tool.

I use Aris Express and Microsoft Visio also but any diagramming tool should have at least partial support to UML.

OK, this is my short tutorial for UML diagram types in the business area. If you have any other ideas how to use UML in a simple way – you can share via comments or send me mail via the contact form.

And if you need some information for Network Diagram Software – visit this article also. It is not pure UML but can be helpful also.