The Quality Wheel

You know quality when you see it, right? Or maybe when you smell it. Like a good perfume. Perfume preferences are different for everyone, and quality means something different for every application.

In perfume, we can discover and describe our preferences using the Fragrance Wheel. This is a spectrum of scent categories, providing a vocabulary for describing each perfume, the attributes of a scent.

Perhaps a similar construction could help with software quality?

When a developer talks about quality, we often mean code consistency and readability, plus automated testing. A tester means lack of bugs. A designer means a great UI, a user means great experience and exactly the right features and lack of errors or waiting. An analyst means insightful reporting and the right integrations, a system administrator means low CPU usage and consistent uptime and informative logging. Our partners mean well-documented, discoverable APIs and testing tools.

Each of these are attributes of quality. For any given software system and for each component, different quality attributes matter most. What’s more, some aspects of quality compliment each other, each makes the other easier – for instance, a good design facilitates a great user experience. Readable code facilitates lack of bugs. Consistent uptime facilitates lack of waiting. Beautiful (consistent, modular, readable) code facilitates all the externally-visible aspects of quality.

However, other aspects of quality are in conflict. Quantity of features hurts code readability. More integrations leads to more error messages. Logging can increase response time.

If we add nuance to our vocabulary, we can discuss quality with more detail, less ambiguity. We can decide which attributes are essential to our software system, and to each piece of our system. Make the tradeoffs explicit, and allocate time and attention to carefully chosen quality attributes. This gets our system closer to something even greater: usefulness.

The quality wheel pictured above is oversimplified; it’s designed to parallel the original version of the Fragrance Wheel. I have a lot more quality attributes in mind. I’d love to have definitions of each piece, along with Chinese-Zodiac-style “compatible with/poor match” analysis. If this concept seems useful to you, please contribute your opinions in the comments, and we can expand this together.