Writing Good Requirements – The Big Ten Rules | Tyner Blain
Pragmatic Marketing has a training seminar called Requirements That Work. In support of that, they provide a list of 8 characteristics of good requirements. We change one and add two more to round it out to The Big Ten Rules. Combine this with Michael’s ten tips for writing MRDs, and we’ve got a good handle on how to create a great MRD.
Pragmatic’s List (1-8) + Two Three Four More
- Necessary Valuable
- Concise
- Design Free
- Attainable
- Complete
- Consistent
- Unambiguous
- Verifiable
- Atomic
- Passionate
- Correct
- Stylish
Looking at each rule of writing good requirements…
1. Valuable
Updated for 2009
Writing valuable requirements is important. It doesn’t matter how well your teams execute if they are off building the wrong products / capabilities / features. The right products and capabilities are the ones that have relevant value.
- Valuable requirements solve problems in your market.
- Valuable requirements support your business strategy.
- Valuable requirements solve problems for your users.
- Valuable requirements meet your buyers’ criteria.
- Valuable requirements don’t over-solve the problems.
Pragmatic uses necessary as a criteria of good requirements. We believe that valuable requirements are good requirements. When prioritizing requirements, we should do the must-have requirements first. But other valuable requirements are critically important – even if they aren’t mandatory. Prioritization and release scheduling should stress necessary requirements first, and then the most valuable requirements next.
Requirements that can differentiate our product from the competition are by definition not necessary – or the competition would have done it already.
[Update: Our detailed article on Writing Valuable Requirements ]
2. Concise
Updated for 2009
Concise requirements give your team a useful, easy to read and easy to change understanding of what must be done. Great requirements exist to do three things:
- Identify the problems that need to be solved.
- Explain why those problems are worth solving.
- Define when those problems are solved.
Easy to read and understand. If only it were that easy. For whom is it easy to read? A market requirements document (MRD) is written for several different people on the team. It provides a vision of what problems our product solves. It provides clarification to the implementation team. It also sets expectations with stakeholders. Different people on the team have different domains of expertise – we have to write requirements that are easily understood by all of them.
[Update: Our detailed article on Writing Concise Requirements]
3. Design Free
Updated for 2009
Design-Free requirements are important for two reasons, and hard for two other reasons.
Design-free requirements are hard because you “know what you want” when you should be documenting “why you want it.” Writing design-free requirements can be hard when you don’t trust your development team to “do the right thing” even though it is not your job to design the solution.
Generally, a requirement should not specifiy any of the implementation choices. From a product manager’s perspective the requirement is the ‘what’ and the spec is the ‘how’. To a system designer or architect or lead developer, the requirement serves as a ‘why’.
[Update: Our detailed article on Writing Design-Free Requirements]
4. Attainable
Updated for 2009
Unless you live in a world filled with unicorns and rainbows, writing realistic requirements is critical. When you set unattainable goals, the best result you can hope for is a frustrated engineering team. Write requirements that are attainable, and your team will surprise you with what they can achieve.
The requirement must be realistically achievable. Barbara and Steve make great points about understanding the cost of implementing something as expressed in the requirements. As we pointed out in our thoughts about good requirements management, there is an optimal tradeoff between costs and benefits for any given company or project. We can formally approach this using the techniques identified for more is better requirements using a Kano framework. In short, the investment must have an ROI that exceeds the opportunity costs by the hurdle rate.
Looking at cost-benefit tradeoffs also supports the argument that valuable should replace necessary.
[Update: Our detailed article on Writing Attainable Requirements]
5. Complete
Updated for 2010
You give your requirements to the engineering team, and they look complete. The team builds your product, you launch it and the market soundly rejects it. Why? Because your requirements weren’t complete – they didn’t actually solve the problem that needed to be solved.
Simply put, if the requirement is implented as written, the market need is completely addressed. No additional requirements are required. When writing a specification, we may use decomposition to break individual requirements into more manageable, less abstract criteria.
[Update: Our detailed article on Writing Complete Requirements]
6. Consistent
Updated for 2010
Consistency in writing requirements is important on two levels – strategic and tactical. Tactically, you need to write your requirements with grammatical consistency, so that potentially ambiguous statements will be interpreted similarly. You also need to write requirements that are logically consistent, so that you avoid “impossible” requirements and gaps of unspecified meaning. Strategically, your requirements need to reflect a focus on markets and problems that are consistent with your business objectives and the vision your company is manifesting
Pragmatic Marketing highlights that the requirement must be logically consistent with the other requirements in the document – no overlaps, no contradictions, no duplications. This is certainly the most important point of consistency.
There is also benefit to consistent writing in an MRD. We can use templates to provide a consistent framework, but more importantly the prose needs to be consistent. This consistency makes it easier on the readers.
[Update: Our detailed aricle on Writing Consistent Requirements]
7. Unambiguous
Updated for 2010
Writing unambiguous requirements is about understanding what is written, and what is read. Without a clear understanding of your market, you can’t write unambiguously. Even when you understand your market, you risk writing something that is ambiguous to your readers. Documenting requirements is about communication. Don’t break this rule, or you’ve wasted all the energy you spent understanding your requirements.
A great requirement has a single interpretation. A good requirement has a single reasonable interpretation. As part of our development process, we will use listening skills like active listening to make sure that our engineering team understands the requirement we intended to write. The better the requirements, the less expensive and risky this communication process will be. Writing unambiguously is critically important when using outsourcing models that limit our interactions with other team members.
[Update: Our detailed article on Writing Unambiguous Requirements]
8. Verifiable
Updated for 2010
Writing Verifiable Requirements should be a rule that does not need to be written. Everyone reading this has seen or created requirements that can not be verified. The primary reason for writing requirements is to communicate to the team what they need to accomplish. If you can’t verify that what the team delivered is acceptable, neither can the team. This may be the most obvious of the rules of writing requirements – but it is ignored every day.
We use a process that starts with market requirements, and then decomposes them into software requirement specifications. the market requirements must be written in a way that we can verify that the associated requirements specification will meet the market need.
[Update: Our detailed article on Writing Verifiable Requirements]
9. Atomic
Updated for 2010
Each requirement you write represents a single market need, that you either satisfy or fail to satisfy. A well written requirement is independently deliverable and represents an incremental increase in the value of your software. That is the definition of an atomic requirement. Read on to see why atomic requirements are important.
Every requirement should be a single requirement. If we can say “Half of this requirement is implemented” then this needs to be two or more requirements. If a requirement read “Sales reps can manage their client list and generate custom reports” it expresses two atomic ideas (list management and report generation). Those ideas need to be separated
[Update: Our detailed article on Writing Atomic Requirements]
10. Passionate
Nothing great has been born from complacency, lethargy or mediocrity. When we are defining requirements, we must be passionate about what we’re doing. If we’re just going through the motions, it shows up in the writing. If we aren’t excited about a requirement, the problem is either with us or with the requirement. Either way, it won’t inspire the rest of the team to do something great.
[Update: Our detailed article on Writing Passionate Requirements]
11. Correct
[Update: Added 30 Oct 2006]
In addition to all of the analyses above, a requirement must actually further the objective it supports, and must be neccessary to meeting that objective, given a particular approach to solving the problem.
Our detailed article on Writing Correct Requirements.
12. Stylish
[Update: Added 5 Jan 2007]
Style can also be the difference between a well-crafted requirement and one that is hard to read. And style, applied consistently across requirements makes it easier to view them as a whole, and identify gaps and inconsistencies. This ease of comprehension matters when trying to achieve correct, consistent, complete requirements.
Our detailed article on Writing Stylish Requirements.
Summary
There isn’t really anything to summarize – this article is one big summary.
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Thank you very much!
Scott
Writing Good Requirements – The Big Ten Rules | Tyner Blain.
