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RE: Additional WebDAV Requirements?

From: Babich, Alan <ABabich@filenet.com>
Date: Mon, 3 Aug 1998 11:37:58 -0700
Message-ID: <72B1992276A9D111A20E00805FEAC96D01324CBC@cm-expo1.filenet.com>
To: "'Bruce Cragun'" <BCragun.ORM2-1.OREM2@gw.novell.com>, fielding@kiwi.ics.uci.edu, francis@netscape.com
Cc: w3c-dist-auth@w3.org
Bruce:

What I have to say has already been stated in this
e-mail thread, but let me try to restate it in a
way that might help.

* Access to the resource itself (and, perhaps, to its 
properties individually) is controlled by the ACL(s)
of the resource and the credentials of the client. 
This is done automatically under the covers, so that 
it is invisible to the operation of normal clients.

* Normal clients do not want to see ACL's, even if
they request "allprop", i.e., return all properties
of a resource. Only security administrators want
to get at the ACL's. For everyone else, ACL's should 
be invisible.

* Aside from not wanting to bother clients with ACL's,
there is a much more serious problem with treating
ACL's as normal properties -- the problem of infinite
regression. For example, ACL's can be used to secure
properties individually. If you treated ACL's
as normal properties on a system that had security
on an individual property basis, you would need a 
second ACL "property" to control access to the first ACL 
"property", which in turn controls access to a normal 
property (say, Author). But of course, the second ACL 
for Author would have to be accessible for modification
as a normal property as well. But you have to control
access to the second ACL for Author. So then you would 
have to have a third ACL property to control access
to the second ACL property, etc. ad infinitum.

The infinite regress problem exists even if there is 
only a single ACL property for the resource as a whole.

* The most obvious solution is to have a separate
access mechanism for ACL's -- treating ACL's exactly
the same as normal properties won't work. This is
not surprising, since they don't perform the same
function as normal properties -- they control access
to normal properties, which is functionality of a
qualitatively different kind. This has nothing
to do with the size of ACL's, or the sharing (or not)
of ACL's across resources by referring to them, or 
design principles (other than "the design must work").

Alan Babich

> I'm not sure I understand why this would be a big mistake.  
> Are you envisioning having a "set" of ACLs that are, in 
> essense, registered, and each resource that has an ACL simply 
> points to an ACL resource?  Or do you consider ACLs to be 
> potentially large and therefore you don't want to use the 
> storage space to store an ACL individually for each document? 
>  Or is it simply a design principle that an ACL should not be 
> a property?
Received on Monday, 3 August 1998 14:41:15 GMT

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