Subject: RE: [Simple] immediate notify issue

From: "Christian Huitema" <[email-masked]>
Date: Mon, 5 Mar 2001 08:50:32 -0800

> you obviously know more than I about this example.
> I would love to see you describe MSN Messenger's responses in 
> the following cases where a WATCHER subscribes to a PRESENTITY:
> 
> 1) PRESENTITY is offline, and has said that anyone can watch him
> 
> 2) PRESENTITY is offline, and has said that only a limited 
> list, which does
>     not include WATCHER, can watch him
> 
> 3) PRESENTITY is online, and answers NO to a request for subscription
> 
> 4) PRESENTITY is online, and answers YES to a request for subscription
> 
> 5) PRESENTITY is online, but has left terminal unattended for an hour.
> 
> In particular, what does the WATCHER know, and when does he know it?

If you run Messenger, you can check several privacy options (click on
the Tools menu, then options, then selecte the Privacy tab.) The options
are organized with two lists and a checkbox:

1) the "allow" list of people who "can see my online status, can send me
messages."
2) the "block" list of people who cannot see my status and cannot send
me messages.
3) the checkbox that tells whether I should be alerted when someone
tries to contact me.

If you click this checkbox, those who try to contact you will not
receive any response until you come on line and make a decision. The
existence of this feature is a serious proff that "just having a piece
of CPL in the server" is not good enough.

Messenger also has an "appear offline" option, that let you appear off
line, even if you are actually loged on. Basically, Privacy is one of
the most important feature of any serious IM system -- you shall not
compromise it in any way.

-- Christian Huitema

---

From: Harald Alvestrand <[email-masked]>
Date: Mon, 05 Mar 2001 19:52:56 +0100

At 08:50 05/03/2001 -0800, Christian Huitema wrote:
>the Tools menu, then options, then selecte the Privacy tab.)

I don't run Messenger, so I have to guess...

>  The options

I see here that there is no real separation between the concepts of a 
WATCHER and a SENDER (in RFC 2778 terms).
I guess that "when someone tries to contact me" also includes "when someone 
tries to subscribe or poll my PRESENCE INFORMATION".

>of CPL in the server" is not good enough.

it depends on what the CPL is allowed to do....

 > 1) PRESENTITY is offline, and has said that anyone can watch him
if checkbox unmarked: subscription accepted < 1 second
if checkbox marked: no response
 >     not include WATCHER, can watch him
if checkbox unmarked: subscription rejected < 1 second
if checkbox marked: no response
 > 3) PRESENTITY is online, and answers NO to a request for subscription
subscription rejected > 1 second
 > 4) PRESENTITY is online, and answers YES to a request for subscription
subscription accepted > 1 second
 > 5) PRESENTITY is online, but has left terminal unattended for an hour.
no response

if this is correct, a WATCHER can know in all cases whether or not the
checkbox is marked (by the speed of response), if he knows a time when the
PRESENTITY is certainly offline.
A WATCHER can also detect (by polling) roughly when a PRESENTITY comes 
online, by noticing when his requests get rejected instead of disappearing 
in a black hole.

if there is no response in 3), the situation is more ambiguous.

>compromise it in any way.

I would implement this as controlling what the PRESENTITY tells the 
PRESENCE SERVICE....this is simpler than telling the PRESENCE SERVICE that 
you are online, but want to appear offline...

--
Harald Tveit Alvestrand, [email-masked]
+47 41 44 29 94
Personal email: [email-masked]