Indicative Words for the Requirements

As practice shows just several words are used to signify the requirements in the specification across different standards. These words are often capitalized. This post copies important definitions of these words as they recommended be interpreted in requirements documents due to long and successful use of this approach bu the author of this post. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this post are to be interpreted as described in RFC 2119.

1. MUST

This word, or the terms “REQUIRED” or “SHALL”, mean that the definition is an absolute requirement of the specification.

2. MUST NOT

This phrase, or the phrase “SHALL NOT”, mean that the definition is an absolute prohibition of the specification.

3. SHOULD

This word, or the adjective “RECOMMENDED”, mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.

4. SHOULD NOT

This phrase, or the phrase “NOT RECOMMENDED” mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label.

5. MAY

This word, or the adjective “OPTIONAL”, mean that an item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.)

Share this post

Share on facebook
Share on linkedin
Share on twitter
Share on email
Share on telegram
Share on whatsapp

Subscribe and stay posted

Fresh updates on all the new posts

Read more posts

Functional safety
Safety

Safety Measures at Glance

In order to achieve functional safety for an item it is important to apply relevant risk reduction measures for those hazardous events that have an unacceptable level of risk (which

Read more
functional safety
Safety

Functional Safety at Glance

Regardless of your industry, if you’re an engineer then I’m pretty sure you’ve encountered the term “Functional Safety” at least once in your career. And I bet you thought at

Read more

Book your free call right now!

functional safety

Message us

Let us know how can we help you and we will get back to you shortly!