Several words are used to signify the requirements of the standards. These words are capitalized. This section defines how these special words should be interpreted. The interpretation has been copied from Internet Engineering Task Force RFC 2119.
|
WORD |
DEFINITION |
|
MUST |
This word or the term "SHALL", mean that the item is an absolute requirement |
|
MUST NOT |
This phrase, or the phrase "SHALL NOT", means that the item is an absolute prohibition |
|
SHOULD |
This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore the item, but the full implications must be understood and carefully weighed before choosing a different course |
|
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 |
|
MAY |
This word, or the adjective "OPTIONAL", means that the item is truly optional. One product team may choose to include the item because a particular type of user requires it or because the product team feels that it enhances the product while another product team may omit the same item |