Add the following text to the exposition on /s:Envelope/s:Body/*/wse:Filter after the second paragraph:

It is possible for the request to contain a filter that will not evaluate to true for the lifetime of the Subscription. Although this condition cannot be detected for all dialects, implementers are advised to check for it when possible and OPTIONALLY generate a wse:EmptyFilter fault.

Add the following fault definition to Section 6:

6.8 EmptyFilter

This fault MAY be generated when an Event Source detects a wse:Subscribe request containing a filter that, for whatever reason, will never evaluate to true.

[Code] s12:Sender
[Subcode]
wse:EmptyFilter
[Reason]
The wse:Filter would result in zero Notifications
[Detail]
The wse:Filter value.