In Requirements, Accuracy Isn’t Enough

Allow me to reflect and maybe even toot my own horn here for just a second. Since I’ve been a business analyst, I think it’s fair to say that I’ve written accurate requirements. By this I mean that they have accurately represented what a user needed to be able to do, and what the system needed to be able to do to meet the business requirements. Despite my presumed accuracy, I’ve faced projects where there has seemed to be an inordinate amount of churn around the wording and language used in expressing requirements – sometimes to seemingly annoyingly inane levels (“Hmmm… That all depends on what the meaning of ‘is’ is….”). Especially as a younger BA, I couldn’t understand why the designers and testers couldn’t understand plain English and just do what the requirements said.

Well, years and experience have tempered me somewhat, and although I still have room for improvement in a lot of areas, one concept has helped me improve a great deal as a business analyst. It has also helped me to understand the angst of the QA analyst and design architect. Today, I’d like to pass it on to those who may benefit from the same lesson. That is:

It’s not enough for requirements to be accurate, they must also be precise.

What is the difference, you ask? Have a look at the image below.

Image above originally sourced from

Accuracy, as you can see on the examples on the right side of the image above, is hitting close to the target. Precision, as evidenced in the top left and lower right examples, is consistently hitting close to the same spot. Obviously, both are important, and the good BA must strive for requirements that are accurate and precise.

So, while I was writing accurate requirements, I was only meeting half of my obligation to downstream delivery teams. To be a good business analyst, I need to communicate in terms that are not only accurate but clear and consistent.

Natural language is inherently ambiguous

The odds are stacked against the BA when it comes to writing requirements that are both accurate and precise, as natural language is inherently ambiguous. The same phrase, punctuated or intoned differently can take on a variety of meanings. For example,

“I, John Doe, am glad to see you here!”

Am I John Doe, and telling someone ( or maybe even a group of people) that I am happy to see him (/her/them) here, or am I addressing myself to John Doe and telling him I am glad to see him here? The statement is accurate, and both are are valid interpretations of the sentence, but only one is the correct result. This is an example of the difficulty I was experiencing with my “accurate requirements”. Different people can understand the same phrase differently depending on the individual and the context. So, how does a BA cope with this?

Some shops adopt different, more precise ways of expressing requirements such as UML, pseudo code, and formal specification language. Here are a few examples of alternatives and how they compare to natural language requirements:

  • Natural Language which includes your typical “user shall” or “system shall” requirements. These are considered the most “understandable” because natural language is the language in which we speak and write. In theory, anyone who can read the language should be able to understand what the requirements are saying. For example, a business stakeholder who has no technology experience, and doesn’t care to bother learning UML or more precise forms of specification will prefer natural language requirements. In my experience, we pretty much always write up our business requirements in this way – be it just a list including vision and objectives, a few user stories, or whatever the case may be. As we mentioned before, natural language is the most open to multiple interpretations and hence the least precise method.
  • Structured Languages like UML that represent natural language through the use of graphics and rules within a structure where each element has a distinct meaning. The symbols and notation rules in UML allow for it to be a more precise means of expressing requirements. UML is still relatively easy to understand, but not as easy as natural language as it does require a little bit of study or training to understand the ins-and-outs. UML diagrams – especially activity diagrams and use case diagrams – are a great alternative to natural language as a way of expressing user and functional requirements.
  • Pseudo Code, or more descriptive languages include if/then/else and other logical statements that read as much like code as they do natural language. It doesn’t necessarily resemble any one particular programming language, but uses common syntax and attributes that allow it to be flexible across technologies. Again, the rules, conventions, and structure of this type of method makes it very precise, although very difficult to read for those that aren’t familiar with the language and logic of software development. Detailed system and design specs are most likely to include this type of language.
  • Formal specification language goes a step beyond pseudo code to include mathematical logic and a code-like format. I’ve never been in an environment that uses this type of specification, but I’ve been told that it is common in aerospace and weapons technology – where lives are at stake, and precision is of the utmost importance – and the user group is familiar with the technical terminology. If you’re curious, here is a link to a page that describes some of the syntax of formal specification language below. Wikipedia also has a worthwhile entry. This link describes the different types of formal specification languages. I’ll also give an example just to emphasize the low-understandability aspect.

Delete(Insert(s, e), e’) ==
if e=e’
then Delete(s, e’)
else Insert(Delete(s, e’), e);

How do I write accurate and precise requirements?

This post is addressed chiefly to the good, old natural language requirement writer, though. Given that natural language is the least precise method of expressing requirements, and given that we need to increase the precision of our requirements for them to be of good quality and use to their consumers, what do we do?

We make our requirements reliable. We make them consistent in form and structure. We adopt a limited, well-understood vocabulary and stick to it. We make our requirements “boring”. This allows us to ensure that each arrow (requirement) is hitting very close to the last. It gives us precision in addition to our accuracy. I have some ideas on how to standardize requirements and make them more consistent and precise, but I’m getting a little long-winded here, so I think I’ll share those in a different entry.

My main point here, and I hope I’ve been able express it adequately, is that the business analyst’s job is not complete if the requirements are written and accurate but not precise. The key is to find a way of articulating requirements that is as precise and as easy to read by the target audience as possible. I’ve found that as my requirements become more precise, the churn around language and semantics decreases significantly. I suspect that many BA’s may find the same to be true.

Anyway, look for follow-on posts in the coming days that will address requirement structure, requirement vocabulary, and any other tricks of the trade I’ve picked up that I think worthwhile to pass along.

In the meantime, take a quick look back at the image detailing accuracy vs. precision. I found it interesting to briefly contemplate the ways that writing precise but not accurate, or accurate but not precise requirements could impact a project.

As always, I’ll be glad for any comments or experiences that you may have had in dealing with issues of accuracy and/or precision in your requirements.