Sunday, August 07, 2016

What Is Quality? Why Is It Important?

(This post is taken from the beginning of Chapter 1 of Book 1 of my Quality Sofware Series: How Software is Built.)

"You can fool all of the people some of the time, and some of the people all of the time, but you can't fool all of the people all of the time."- Abraham Lincoln
People in the software business put great stress on removing ambiguity, and so do writers. But sometimes writers are intentionally ambiguous, as in the title of this book. "Quality Software Management" means both "the management of quality software" and "quality management in the software business," because I believe that the two are inseparable. Both meanings turn on the word "quality," so if we are to keep the ambiguity within reasonable bounds, we first need to address the meaning of that often misunderstood term.
1.1 A Tale Of Software Quality
My sister's daughter, Terra, is the only one in the family who has followed Uncle Jerry in the writer's trade. She writes fascinating books on the history of medicine, and I follow each one's progress as if it were one of my own. For that reason, I was terribly distressed when her first book, Disease in the Popular American Press, came out with a number of gross typographical errors in which whole segments of text disappeared (see Figure 1-1). I was even more distressed to discover that those errors were caused by an error in the word processing software she used—CozyWrite, published by one of my clients, the MiniCozy Software Company.
The next day, too, the Times printed a letter from "Medicus," objecting to the misleading implication in the microbe story that diphtheria could ever be inoculated against; the writer flatly asserted that there would never be a vaccine for this disease because, unlike smallpox, diphtheria re-

Because Times articles never included proof—never told how people knew what they claimed—the uninformed reader had no way to distinguish one claim from another.
Figure 1-1. Part of a sample page from Terra Ziporyn's book showing how the CozyWrite word processor lost text after "re-" in Terra's book.

Terra asked me to discuss the matter with MiniCozy on my next visit. I located the project manager for CozyWrite, and he acknowledged the existence of the error.
"It's a rare bug," he said.
"I wouldn't say so," I countered. "I found over twenty-five instances in her book."
"But it would only happen in a book-sized project. Out of over 100,000 customers, we probably didn't have 10 who undertook a project of that size as a single file."
"But my niece noticed. It was her first book, and she was devastated."
"Naturally I'm sorry for her, but it wouldn't have made any sense for us to try to fix the bug for 10 customers."
"Why not? You advertise that CozyWrite handles book-sized projects."
"We tried to do that, but the features didn't work. Eventually, we'll probably fix them, but for now, chances are we would introduce a worse bug—one that would affect hundreds or thousands of customers. I believe we did the right thing."
As I listened to this project manager, I found myself caught in an emotional trap. As software consultant to MiniCozy, I had to agree, but as uncle to an author, I was violently opposed to his line of reasoning. If someone at that moment had asked me, "Is CozyWrite a quality product?" I would have been tongue-tied.
How would you have answered?
1.2 The Relativity of Quality
The reason for my dilemma lies in the relativity of quality. As the MiniCozy story crisply illustrates, what is adequate quality to one person may be inadequate quality to another.
1.2.1. Finding the relativity
If you examine various definitions of quality, you will always find this relativity. You may have to examine with care, though, for the relativity is often hidden, or at best, implicit.
Take for example Crosby's definition:
"Quality is meeting requirements."
Unless your requirements come directly from heaven (as some developers seem to think), a more precise statement would be:
"Quality is meeting some person's requirements."
For each different person, the same product will generally have different "quality," as in the case of my niece's word processor. My MiniCozy dilemma is resolved once I recognize that
a. To Terra, the people involved were her readers.
b. To MiniCozy's project manager, the people involved were (the majority of) his customers.
1.2.2 Who was that masked man?
In short, quality does not exist in a non-human vacuum.
Every statement about quality is a statement about some person(s).
That statement may be explicit or implicit. Most often, the "who" is implicit, and statements about quality sound like something Moses brought down from Mount Sinai on a stone tablet. That's why so many discussions of software quality are unproductive: It's my stone tablet versus your Golden Calf.
When we encompass the relativity of quality, we have a tool to make those discussions more fruitful. Each time somebody asserts a definition of software quality, we simply ask,
"Who is the person behind that statement about quality."
Using this heuristic, let's consider a few familiar but often conflicting ideas about what constitutes software quality:
a. "Zero defects is high quality."
1. to a user such as a surgeon whose work would be disturbed by those defects
2. to a manager who would be criticized for those defects
b. "Lots of features is high quality."
1. to users whose work can use those features—if they know about them
2. to marketers who believe that features sell products
c. "Elegant coding is high quality."
1. to developers who place a high value on the opinions of their peers
2. to professors of computer science who enjoy elegance
d. "High performance is high quality."
1. to users whose work taxes the capacity of their machines
2. to salespeople who have to submit their products to benchmarks
e. "Low development cost is high quality."
1. to customers who wish to buy thousands of copies of the software
2. to project managers who are on tight budgets
f. "Rapid development is high quality."
1. to users whose work is waiting for the software
2. to marketers who want to colonize a market before the competitors can get in
g. "User-friendliness is high quality."
1. to users who spend 8 hours a day sitting in front of a screen using the software

2. to users who can't remember interface details from one use to the next

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