A process flow (business flow or workflow) diagram maps out everything that's required to get from point A to point B. It shows the steps in a process, the users involved, inputs, outputs and decisions. As a result, it's a very powerful tool to illustrate what you want your online platform or app to do.

In this article, I'll explain the different parts of a process flow diagram, show you an example, and tell you why you should use them to describe what you want your product to do.

A process flow diagram consists primarily of 6 parts:

1. Start and end points: these are points where the process starts and ends.
2. Steps: these are the individual activities for taking a user from the start point to the end point.
3. Users (and systems): these are all of the people and applications involved in the process.
4. Inputs: these are all of the things that need to be contributed to the process to complete the task. This might be information, documents, images or anything else that is required.
5. Outputs: this is anything that comes out of the process. It can be physical (like a document) or digital (like a search result list or an online message to confirm payment) or maybe its emotional (like the satisfaction of finishing a game)
6. Decisions: these are all of the choices that need to be made by a user to get from the start point to the end point. They may also be conditions that result in a user being diverted in a different direction.

All of these parts join together to create your process flow diagram.

Now, I'll show you how all of those pieces fit together to create a process flow diagram.  This example is for subscribing to a newsletter.

A couple of things to note here. Firstly, there are lots of different ways to draw this diagram. It doesn't matter which one you use - in fact, it doesn't matter if you follow the rules and syntax at all - as long as your developers and any other people involved in your project interpret your diagram correctly.

Secondly, some processes have steps that could have many steps within them - you could very easily go down two or three levels as you flush out what happens in a step. However, like writing your requirements, there's an art to figuring out the level of detail that you should go to. At some point, the effort required to create the diagram outweighs the benefit. You might eventually need to get down to that level of detail to build your platform or app, but when describing what your product should do, it's probably not necessary.

While process flow diagrams can be used to map out anything that people do (e.g. call centre operations, consulting engagements, opening a bank account, etc), they are particularly  powerful when developing online platforms and mobile apps. Along with wireframes, they help to illustrate your vision to the people that will help you bring it to life. These diagrams represent a language that developers can understand and they show key concepts - without having to do a lot of writing.

Process flow diagrams also help you to flush out your product. Platforms and apps have a lot of moving parts, so if you can identify all of the processes in your product, you'll get a good idea of what needs to be built. From there, you can expand on each process to  define what you want your product to do.

Finally, using process flow diagrams will give you a more complete picture of your platform or app, and puts context around your product requirements. With more information, your developer is now in a better position to give you a more accurate estimate for building your product.