Subject: [Simple] question on presrules

From: Enrique Izaguirre <[email-masked]>
Date: Thu, 07 Feb 2008 15:46:17 +0100

Hi,

according to RFC5025 there could be scenarios where the transformations 
within a matching ruled whose action=block may filter the presence 
document showed to the requestor.

E.g. this can happen when there are two matching rules, one that is 
blocking and the other is allowing, and they have different 
transformation elements. If RFC4745 is applied, the combined action is 
"allow" and the combined transformation is a superset of both 
"transformations".

So, is the assumption that clients are smart enough so they will never 
fall into the above case? or should a presence server prevent clients 
from not doing such combination of rules?

Thanks and regards,
Enrique.
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---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 11 Feb 2008 21:29:18 -0500

> "allow" and the combined transformation is a superset of both 

Right. That is a possibility.

> from not doing such combination of rules?

Its a job of the UI on the client to prevent this. Normally its not a 
problem. The spec has this to say:

A consequence of this design is that the results of combining several
    authorization documents can be non-obvious to end users.  For
    example, if one authorization document grants permission for all
    users from the example.com domain to see their presence, and another
    document blocks [email-masked], the combination of these will still
    provide presence to [email-masked].  Designers of user interfaces
    are encouraged to carefully pay attention to the results of combining
    multiple rules.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   499 Thornall St.
Cisco Fellow                                   Edison, NJ 08837
Cisco, Voice Technology Group
[email-masked]
http://www.jdrosen.net                         PHONE: (408) 902-3084
http://www.cisco.com
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