The RFC 2119 terms "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" are meant to
apply to specific requirements and behaviors within the context of a
specification. They are *not* meant to refer to general concepts and actions.

To quote RFC 2119: "Imperatives of the type defined in this memo must be used
with care and sparingly.  In particular, they MUST only be used where it is
actually required for interoperation or to limit behavior which has potential
for causing harm (e.g., limiting retransmisssions)"

WS-Transfer contains a number of cases where RFC 2119 keywords are
misused. A changebar copy of WS-Transfer will be sent to the mailing list and
linked in the comments below.