Using Focus Words in Your Requirements

Let’s look at the focus words we commonly use in our requirements documents. Requirements use many words to signal their focus and intent, such as ‘will’, ‘must’, ‘may’, ‘can’, ‘shall’, or ‘should’. There are some legal ramifications to certain focus words if they appear in a written contract. These concerns may govern what words can be used in what document regardless of what word the business analysts on the project team might prefer to use. 

The IEEE looks at focus words in their standards style manual at http://standards.ieee.org/guides/style/section5.html. Here’s a quick summary of their recommendations:

  • ‘Shall’ indicates a mandatory requirements to be met, and implies ‘is required to’
  • ‘Should’ indicates the preferred possibility of several recommended options, and implies ‘is recommended that’
  • ‘May’ indicates a permissible course of action, and implies ‘is permitted’
  • ‘Can’ is used for statements of possibility and capability, and implies ‘is able to’
  • Do not use ‘may’ and ‘can’ interchangeably – reserve ‘may’ for the permissibility of doing something, and ‘can’ for the capability.
  • ‘Must’ is not to be used as an alternative to ‘shall’. This focus word is used only to describe unavoidable situations or perhaps used in business rules. Many times, ‘must’ identifies a legislative or regulatory requirement (e.g. health and safety) which shall be complied with.
  • ‘Will’ is used in statements of fact versus being part of the actual requirements.

 I like the IEEE perspective on focus words, and use it on many of my more formal requirements development efforts.

Of course, there is another approach to the focus word dilemma –use a plain technical writing style. Plain style does not use any focus words! The subject is simply the ‘doer’ of the verb in a statement defining a capability. For example, “The user shall locate a course title within five seconds.” becomes “The user locates a course title within five seconds.” Pretty cool, eh? Of course, some folks just don’t think it is a requirement if there isn’t at least one ‘shall’ in there somewhere!

Susan Weese

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