Don't Overlook the Adjectives in User Stories
Posted by kenhoward on December 19, 2008
Take a look at two versions of a User Story, which are written using Mike Cohn’s popular format:
As a customer service rep, I can calculate a customer’s account balance so I can provide it when a customer calls to request it.
As a customer service rep, I can easily calculate a customer’s account balance so I can promptly provide it when a customer calls to request it.
There are two words added in the second version of this User Story that could potentially derail the development effort if ignored. It’s easy to overlook adjectives and adverbs as adornments that don’t add value. While version 1 emphasizes a functional requirement of the system, those two little words added in version 2 specify two non-functional requirements that mustn’t be overlooked.
Out of the box, Scrum and other Agile methods may not sufficiently address the handling of non-functional requirements. The method I have always used for removing ambiguity from non-functional requirements is based on Gerald Weinberg’s writings about system attributes. This also aligns with popular practices of Thomas Gilb.
|Target||Account balance calculation process|
|Measured by||Number of manual steps required|
|Measured by||Time from submit until calculation appears|
|Minimum acceptable||0.5 second|
|Maximum acceptable||3.0 seconds|
By now, the Scrummers out there may be squirming, but hear me out. The exercise of negotiating metrics for non-functional requirements with the Product Owner will likely result in one of two outcomes: 1) They will (painfully) specify the values, or 2) They will cede that they don’t really feel that strongly about the attribute.
I’ve heard of some folks who write user stories written explicitly for a non-functional requirement itself. This could feel like squeezing a square peg in a round hole. A more pragmatic approach would be to simply create a task supporting the user story above to the effect of: “Specify measurement criteria for promptly” and “Specify measurement criteria for “easily”. The deliverable for these tasks could potentially conform to the format I described above.