What is DIRFTTo quote Wikipedia,
Crosby's response to the quality crisis was the principle of "doing it right the first time" (DIRFT). He also included four major principles:
- The definition of quality is conformance to requirements (requirements meaning both the product and the customer's requirements)
- The system of quality is prevention
- The performance standard is zero defects (relative to requirements)
- The measurement of quality is the price of nonconformance
His belief was that an organization that establishes good quality management principles will see savings returns that more than pay for the cost of the quality system: "quality is free". It is less expensive to do it right the first time than to pay for rework and repairs.
Problematic assumptions in DIRFT
#1 - Quality isn't conformance!
Can we assume that people can objectively and comprehensively phrase all requirements at all - much less before validating them against the outcome?
Objectivity: I leave it to you, dear reader, to determine what happens when those who specify, those who implement and/or those who verify the requirement have a different understanding of the others! I then challenge you to create a surefire method of ascertaining this before even beginning with the implementation.
Comprehensiveness: The need for objectivity would force us to create an explicit, comprehensive list of requirements. Remember: "Quality is conformance to requirements" - and if it's not defined, it's not part of quality!
I now challenge you to create a comprehensive list of requirements for even the most mundate item of daily life: a piece of paper! Don't forget that it should be fit to write upon (don't forget to specify the type of ink that may be used and at what temperature - maybe you should also include how the paper should behave when an eraser is used?)
Validation: Validation occurs on many levels, let's just get into the kind that DIRFT is considering implicit: How do you ensure that requirements are specified correct, comprehensive and consistent? Of course, you validate them. So - if you want to build the product right the first time, you have to absolutely and unconditionally ensure that each and every requirement, as well as their entirety, is valid. Only then do you have a chance to meet them.
I leave it to you to figure out a method of ensuring that a product's requirements are exhaustively valid without having even started implementation!
#2 - You can't prevent all defectsDIRFT assumes that all potential sources of defects are known and controllable. That's another two strong assumptions that hardly hold to a practice test. Honestly; what good is a product that is "of high quality" if it simply doesn't work the way the customer expects it to?
Omniscience: There's a proverb, "If you make something foolproof, someone will make a better idiot." Google for "Use for intended use only" - a helpless plea of designers who already realized that once the product is in the customer's hands, people will get ideas that nobody could ever anticipate!
Omnipotence: You may have gotten it completely right, but because the world behaves differently from how designers anticipated, the product still doesn't work. The only way to prevent that kind of defect is by making the product so robust that it'd effectively be omnipotent.
#3 - Zero defects are arbitraryAs explored above, requirements are an incomplete subset of what makes a product valuable, even potentially incompatible with the definition of value. By adding any implicit requirement (such as: "paper shouldn't be lethal to the touch"), the product may appear defective again. The only chance to fix the defect is by making changes - both to the design, and to the product!
Finality: One of the core, hidden and implicit assumptions of DIRFT are that there is ever a point in time where the final design is "known", and that this point in time is before the beginning of implementation.
Perfection: Along with the finality of the design comes the assumption that this design is "perfect" in relation to whatever requirements exist. While one can reasonably argue that a "good enough" design can be procured, one will be hard-pressed to argue that the first attempt will result in a design that leaves no room for improvement anywhere.
#4 - Nonconformance is a pointless measureAs tester, I always found joy in discovering nonconformance - more so, if the nonconformance was somehow "critical". It didn't take me much longer than a few days into my first job to discover that nobody cared for nonconformance in the presence of other business-relevant metrics, such as the cost of delay or the cost of change.
Time-Value discount: The above statements come into play again. With every added requirement, the implementation effort increases. It's possible to conform to 1% of requirements now, and to 100% at an undefined point in the future. Getting it right the first time assumes that the Time-Value discount is Zero. This is diametrically opposed to the idea that "the marginal value of every technology is Zero", i.e. as time progresses, the ROI on technology decreases.
Measuring nothing: The entire hypothesis of "DIRFT" is that somehow, magically, the created product is done right the first time, i.e. the idea of measuring nonconformance is supposed to measure the empty set. Does it sounds odd to anyone else to base a core business metric on an empty set? The mere idea of measuring nonconformance implies that the Crosby is somehow aware that this is a fictional, impractical approach!
Okay, after setting the groundwork that pretty much every single word of "Do it right the first time" relies on unfounded assumptions, let's shred the final conclusion:
Quality is never free!DIRFT assumes that when someone somehow has looked into their crystal ball to create a flawless design of a perfect product and those creating it somehow have all the required time and money on their hands to build something that matches this design, then somehow magically, "quality is free".
Let's ignore even the (infinite) costs for building, and ponder for a minute how much time and money is required to produce the perfect design which then just needs to be "done right". Any design document you produce, I will find at least one unlisted requirement, at least one relevant edge case, at least one "bad case" that can wreck the product. And the longer your requirement document is, the easier this will be.
We end up with "quality is free" only when we invest an infinite amount of time, effort and money into upfront work - otherwise, the entire idea of "DIRFT" isn't even applicable.
"Do It Right the First Time is a nice ideology, but impractical for anyone doing product work, where deadlines, budget constraints and uncertainty about the customer's needs are the key constraints.
In development work, quality is an optimization goal, and while it makes a lot of sense to maximize quality, it is never free - quality is where the money and effort goes!