There are multiple different ways to Cancel a CAP message, each with subtle meanings.
msgType Cancel is more akin to Revoke. Consider renaming, and adding a requirement that Cancel messages do not have an info block.
msgType Cancel could apply to the “event” instead and may be part of the new event information construct for CAP
Current practice in widespread use is to use an info block with a Cancel to explain the reasons for the cancellation. Clarify whether Cancel is appropriate for this case, or should msgType Alert be used. Clarify how to specify expires times in these cases.
Clarify how to use Cancel with responseType AllClear, noting Cancel practices had evolved out of the lack of All Clear in prior CAP versions.