[alto] Issue about incr-updates-sse update stream control design

[Jensen Zhang <[e-mail]>]

Hi incr-update-sse authors and all,

I have a question about the current update stream control design in
incr-updates-sse.

In the last paragraph of Section 7.6.2, the document writes

"When the client uses the stream control service to stop updates for one or
more resources (Section 8
<https://tools.ietf.org/html/draft-ietf-alto-incr-update-sse-09#section-8>),
the ALTO server MUST send a control event (Section 6.3
<https://tools.ietf.org/html/draft-ietf-alto-incr-update-sse-09#section-6.3>)
whose "remove" field has the client-ids of those resources."

As section 7 defines "Update Stream Service", this paragraph means the ALTO
server MUST send a control event in the update stream to notify the client
the status of a stream control service request. Why do we want to use a
different channel to return the output? Why not return this control event
from the response of update stream control service? I feel it will
introduce the unnecessary complexity.

Can anyone of authors elaborate the reason for this design?

Thanks,
Jensen