Usable Software Diagram

“Who is the user of software design”?
Some Software Usable Design practitioners think that the user is the developer.

I think the answer is not the same in every Dimension.

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The user of software design is the developer

Specifically in the Artefact dimension.
Maybe it was the first answer to come in mind, because the question was initially asked by some developers.
The developer uses the design to build a mind map (with abstraction and static representation) of the software. With this map, she is able to navigate through the codebase in order to achieve a feature or to fix a bug.
She will technically explain to the machine how it should behave, but other humans will need to understand these explanations. A good design will give a frame to help the developer to put responsibilities in the good place.developer-512

The user of software design is the final user

Specifically in the Runtime dimension.
If a user has to read our documentation, it is a failure and an opportunity for improvement.
The software design must be crystal clear for the user at Runtime, because she will also build a mind map (with dynamic representation) of the software.
Not the same map than the developer, because it has different purpose. But still the user will navigate in the UI thanks to this map, in order to achieve what is useful to perform her job.

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The user of software design is the business

Specifically in the Decision dimension.
And the whole purpose of DDD is to bring back this reality as soon as it is forgotten in the Artefact or Runtime dimension.
Again, the business build a different mind map (with business use cases), and uses it in order to take decision. The goal is to improve the business using the power of software.

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Navigating with our own map

The map metaphor is really powerful, and Eric Evans himself uses it a lot.

I also like this talk by Simon Brown about the Art of Visualizing Software Architecture. He compares the drawing of an architecture with the drawing of a map. His point is that we need to know for who is our drawing, and why. Because any representation is an abstraction of the full system, and we need to understand what will be done based on our drawing to choose the good abstraction, at the good level.

Software design is used to navigate in the understanding of a software system. For this navigation to be efficient we want:
– a consistent level of abstraction
– abstractions align with our dimensionimages
Usable Software Architecture Design
A Usable Design needs to be navigable.
A good visualisation for our Software Architecture will let us know if our design is usable or not in terms of navigability.
Taking into account the dimension will help to build useful and navigable abstractions, because it implies a specific user in a specific context.

Don’t fall into the trap of mixing scale, or dimensions, in the same drawing. It will only result in a messy diagram that we’re used to see in our enterprises.

Instead choose one scale and one dimension to build understandable diagrams for one purpose.

 

Ouarzy

 

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