1.0.3 Language

There are three levels of obligation with regards to
conformance to the xAPI specification identified by the terms
MUST, SHOULD and MAY. A service or system that fails to

implement a MUST (or a MUST NOT) requirement is non-
conformant. Failing to meet a SHOULD requirement is not a

violation of conformity, but goes against the
recommendations of the specification. MAY indicates an
option, to be decided by the developer with no
consequences for conformity. Usage of these terms outside
of requirement language does not designate a requirement
and is avoided whenever possible.

Updated Language

To align with the IEEE Standards Association (SA)
guidance, xAPI MUSTs were changed to SHALLs
Although MUST is becoming the standard for
requirements in technical specifications, IEEE SA
mandates the use of SHALL. xAPI was updated to
follow IEEE SA guidance at

https://standards.ieee.org/develop/drafting-
standard/write.html Complete definitions of MUST,

SHOULD, MAY, MUST NOT and SHOULD NOT are
found in RFC 2119. IEEE adheres to these definitions.
Note that MUST and SHALL are equivalent.