Section 4.5 "Subscription End" starts with the following paragraph:

"If the event source terminates a subscription unexpectedly, SubscriptionEnd SOAP message SHOULD be sent to the endpoint reference indicated when the subscription was created (see 4.1 Subscribe). This endpoint reference MUST refer to an endpoint that supports the SubscriptionEndPortType portType. The message MUST be of the following form:"

The SHOULD in this sentence is ambiguous. Does it refer to the act of transmitting the message or does it refer to where the message is transmitted? In both cases this should be a "MUST"; the SubscriptionEnd message MUST be transmitted, and it MUST be transmitted to the endpoint referenced by the EndTo EPR.

The sentence "This endpoint reference MUST refer to an endpoint that supports the SubscriptionEndPortType portType" is inappropriate and redundant; this is a constraint on the event sink, not the event source. This same constraint is already documented in the description of /wse:Subscribe/wse:EndTo.

Proposal: replace the above paragraph with the following:

"If the event source terminates a subscription unexpectedly and the wse:EndTo EPR was present in the Subscribe message for that subscription (see 4.1 Subscribe), the SubscriptionEnd message MUST be sent to the endpoint referenced by that EPR. The message MUST be of the following form:"