What is Quality?

May 13, 2010 · 6 comments

How do you define quality? Ford says that quality is job one but what is it and how do we create quality? We all recognize quality service at a fine restaurant and a quality product like a fine piece of furniture but what is quality in software?

I ask this question a lot to developers in my classes. Often I get answers like the software should do what it is supposed to do or it should not be slow and buggy. These things are important but the kind of quality I am talking about is internal quality; how well the software was written.

Software is non-tangible. It is governed by different forces than things in the physical world but it is governed by forces nonetheless. One of the key forces that affect software quality is complexity. When software is overly complex it is prone to bugs.

Some say that because the end user has no direct experience of code quality that quality is not important in software. This is a position maintained by people who have probably not written much software. Just because a piece of software is behaving correctly right now doesn’t mean that it will be easy to add new features to it later. Without the ability to fix bugs or improved a product, users generally lose interest and software generally loses market share.

How do you define software quality? What makes software good and how do we achieve it?

{ 6 comments… read them below or add one }

David Koontz May 14, 2010 at 5:31 pm

Interesting question. But to define software quality without the definition of the overriding product quality is a mistake. Software by itself is not useful, it has little value, and only academic quality. Yes one could discuss the quality of software that is written but not running. But it is only in the intended product (software + hardware) that the quality of the software has meaning. Software quality is a large part of a products quality, but I think it is a mistake to decompose the issue into components, and only discuss one of these components (software). The more interesting question is how does one create a high quality product that contains software? What is required of the hardware and the OS and other components to create an environment where the software can be high quality?

As an example to discuss, compare the iPhone platform to the Blackberry platform, and the environments these platforms have evloved within. I think Apple’s work in creating the simple-complexity of the iPhone platform is a example of quality in the product at the system level. They tried just the software level with the Motorola Razor, but it didn’t work. Hardware is integral to software quality.

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davidbernstein May 17, 2010 at 9:40 am

Hi David,

Thank you for your comment. I agree that product quality is also important. In fact, if we build the wrong stuff, no matter how elegantly, all bets are off. My only point is that just building the right thing isn’t good enough anymore. It used to be when I was starting out in development a quarter century ago but now it is clear that part of what we deliver as developers is the maintainability and extendibility of our software, not just what it does.

In saying this I do not mean we should try to anticipate how our code could be changed in the future. This can lead to paralysis by analysis. But if there are standards and practices we could follow that would make all the code we write more maintainable and extendable then I think those are important for us to follow and to share with others on our team.

Again, I am not saying that we should do this to the exclusion of anything else; a whole product has many components. However, unlike in hardware development, we software developers have relatively few standards and practices that are generally accepted among all of us. This is an area where we, as a profession, need to improve.

Yes, I am a big advocate for code quality but I also know that writing quality code really doesn’t take more time than writing poor code. If we could all agree on a common definition for quality I think we would build better software.

David.

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ian savage May 16, 2010 at 6:43 am

IMO You are on the right track, David: Quality (as perceived by someone) is a function of its many attributes – including features/functionality, usability, reliability, performance, security, scalabilty, maintainability, extensibilty (refactorability?), availability, and others.

Note the word “function.” I believe this function may vary between people depending upon circumstances, needs, and expectation from time to time.

Note also that this is a unbounded list. People may have other important criteria by which they judge software.

Too squishy? Perhaps not. Since quality is a complex formula, operationalizing the attainment of quality is a collaborative effort: What is important for *us* now? What’s important for our customers? For our market? For our business partners? For other stakeholders? What will be important for them next year and throughout the (long) life of this software solution?

Perhaps a nice, pithy one-line defn would be better. But it simply isn’t that simple.

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davidbernstein May 17, 2010 at 9:41 am

Hi Ian,

I couldn’t agree more.

David.

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Sebastián Pilafis June 7, 2010 at 7:12 pm

I like the ideas from Deming, Ishikawa and Crosby in regards to quality, when they say that quality is essentialy free, but the cost of quality is the cost you pay for not doing things right the first time.
From that you can derive all the attributes that you would expect from a good definition.

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davidbernstein June 8, 2010 at 6:01 am

Yes I totally agree, Sebastian. I used to think that investing in quality was something that costs more in the beginning but pays for itself over time. Now I believe that quality is often cheaper in the beginning and is much cheaper in the end. If we make quality our habit it is just as easy to write high quality code as it is to write poor quality code, maybe easier. It is all about the habits we have and the practices we follow, as you know.

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