PART B > FUNCTIONAL SPECIFICATIONS

Interpretation of functional specifications

Individual specifications in Part B of this Standard are grouped according to the clusters from the high-level model in Part A, section 4.

The keywords 'must' and 'should' that appear in the specifications in Part B indicate the relative importance of each specification. These keywords are to be interpreted as follows:¹⁹

Keyword	Interpretation
'must'	Specifications that use 'must' are an absolute requirement for compliance with the Standard.
'should'	Specifications that use 'should' may be ignored if a valid reason exists, but the full implications of ignoring the specification must be understood and carefully weighed before choosing a different course.

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19. Bradner, S. 1997. RFC 2119: Key words for use in RFCs to Indicate Requirement Levels. These definitions in this Standard are based on the definitions from RFC 2119.