Subject: [XCON] Policies in the data model

From: Gonzalo Camarillo <[email-masked]>
Date: Mon, 12 Mar 2007 14:58:12 +0200

Hi,

the biggest open issue in the data model is policies. We need to decide:

1) whether policies (e.g., who can perform certain tasks like adding or 
removing a user) are in or out of the data model's scope.

2) if they are in scope, whether we follow a syntactic (e.g., user A can 
modify element <foo>) or semantic (e.g., user A can add new users to the 
conference) approach.

3) the granularity to use. Whether to have pre-defined roles where 
higher roles are authorized to perform a super set of the operations 
performed by lower roles, or to have groups of users (similar to Unix 
groups).

I would like to encourage people to discuss these issues because, 
otherwise, it will be impossible to make any progress on this field.

Cheers,

Gonzalo

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From: Henning Schulzrinne <[email-masked]>
Date: Mon, 12 Mar 2007 09:03:46 -0400

I'll add that it might be interesting to look at the policy work in  
SIMPLE (common policy, etc.). It takes somewhat of a middle ground,  
with both more semantically oriented permissions and some operations  
that are closer to XML elements, although it probably tries to stay  
on the semantic side rather than, say, specifying Xpaths as permissions.

In my personal opinion, it is very hard to make syntactic permissions  
work well, simply because one often wants to express permissions that  
span multiple elements and that only make sense if expressed as a  
whole. Also, syntactic permissions can easily yield meaningless or  
illegal operations ("remove the parent element that is required").

On Mar 12, 2007, at 8:58 AM, Gonzalo Camarillo wrote:

> 1) whether policies (e.g., who can perform certain tasks like  
> adding or removing a user) are in or out of the data model's scope.
>
> 2) if they are in scope, whether we follow a syntactic (e.g., user  
> A can modify element <foo>) or semantic (e.g., user A can add new  
> users to the conference) approach.
>
> higher roles are authorized to perform a super set of the  
> operations performed by lower roles, or to have groups of users  
> (similar to Unix groups).
>

---

From: Simon Pietro Romano <[email-masked]>
Date: Mon, 12 Mar 2007 16:10:50 +0100

Hi Gonzalo,

I personally have a general concern with respect to this point. By general I
mean that I think that all what concerns rights, roles, constraints etc should
be kept outside of both the data model and the conference control protocol
inner
structure. All these things relate to policy management as a whole and should
be dealt with through the adoption of an integrated (as well as orthogonal to
the data model definition process) approach like XACML, which has been
conceived exactly for this purpose.

Cheers,

Simon
-- 
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   ~~~~~~~~~~~~~~~~~~~~~~o00~~(_)~~00o~~~~~~~~~~~~~~~~~~~~~~~~
                    Simon Pietro Romano
              Universita' di Napoli Federico II
                 Computer Science Department 
        Phone: +39 081 7683823 -- Fax: +39 081 7684219
                e-mail: [email-masked]

    <<Molti mi dicono che lo scoraggiamento è l'alibi degli 
   idioti. Ci rifletto un istante; e mi scoraggio>>. Magritte.
                         oooO
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                          \ (    (   )
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                                 (_/

> otherwise, it will be impossible to make any progress on this field.

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From: Srivatsa Srinivasan <[email-masked]>
Date: Mon, 12 Mar 2007 09:50:20 -0700

I share the same opinion here (which is what made me comment to the original proposal in the first place). I would recommend postponing the decision to sometime after we finalize the data model, the user id drafts, the conference event package and media usages (for the base controls -- mute/pause/layout).

> -----Original Message-----
> From: Henning Schulzrinne [mailto:[email-masked]]
> Sent: Monday, March 12, 2007 6:04 AM
> To: Gonzalo Camarillo
> Cc: XCON
> Subject: Re: [XCON] Policies in the data model
>

---

From: Gonzalo Camarillo <[email-masked]>
Date: Mon, 12 Mar 2007 20:15:05 +0200

Hi Henning,

there is an already expired draft that tried and used the common policy 
language to define a conference's policy.

http://www.watersprings.org/pub/id/draft-niemi-xcon-cpcp-rules-00.txt

Maybe this could be a good starting point. XACML has also been mentioned 
in this thread. It would be interesting if somebody could have a look at 
how XACML could be used for our purposes to see whether or not is a good 
fit.

Regarding my question 1) below, there have been answers in favor and 
against including policy in the data model. We need to discuss this in 
more detail.

Cheers,

Gonzalo

---

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 12 Mar 2007 14:48:00 -0400

Just like SIMPLE data and policy are separate, I see some advantage  
of keeping them separate here as well. Plus, it seems likely that  
(some) policies change much less frequently than other conference  
details. As with any policy discussion, it might be helpful to gain a  
common understanding what all would be included, such as:

- creation of conferences ("can create conferences only from 9 to 5  
on Tuesdays")?

- permissions for changes of conference state ("can become moderator"  
vs. "can designate moderator")?

- resource controls ("can create conferences with no more than 8  
people")

This can get arbitrarily complex.

On Mar 12, 2007, at 2:15 PM, Gonzalo Camarillo wrote:

> Hi Henning,
>
> there is an already expired draft that tried and used the common  
> policy language to define a conference's policy.
>
> Maybe this could be a good starting point. XACML has also been  
> mentioned in this thread. It would be interesting if somebody could  
> have a look at how XACML could be used for our purposes to see  
> whether or not is a good fit.
>
> Regarding my question 1) below, there have been answers in favor  
> and against including policy in the data model. We need to discuss  
> this in more detail.
>
> Cheers,
>
> Gonzalo

---

From: "Oscar Novo \(JO/LMF\)" <[email-masked]>
Date: Tue, 13 Mar 2007 12:03:08 +0100

Hi Srivatsa,

The 04 version of the data model is already aligned with the user id
drafts. The conference user identifier is already defined in that
version.

Cheers,

Oscar

-----Original Message-----
From: Srivatsa Srinivasan [mailto:[email-masked]] 
Sent: 12. maaliskuuta 2007 18:50
To: 'Henning Schulzrinne'; Gonzalo Camarillo (JO/LMF)
Cc: 'XCON'
Subject: RE: [XCON] Policies in the data model

I share the same opinion here (which is what made me comment to the
original proposal in the first place). I would recommend postponing the
decision to sometime after we finalize the data model, the user id
drafts, the conference event package and media usages (for the base
controls -- mute/pause/layout).

> that are closer to XML elements, although it probably tries to stay on

> the semantic side rather than, say, specifying Xpaths as permissions.
>
> > 1) whether policies (e.g., who can perform certain tasks like adding

> > or removing a user) are in or out of the data model's scope.
> >
> > 2) if they are in scope, whether we follow a syntactic (e.g., user A

> > can modify element <foo>) or semantic (e.g., user A can add new 

> > performed by lower roles, or to have groups of users (similar to 
> > Unix groups).
> >

---

From: Gonzalo Camarillo <[email-masked]>
Date: Tue, 13 Mar 2007 13:16:08 +0200

Hi,

 > I would recommend postponing the

the user id stuff and the main media usages (i.e., audio and video) will 
be included in the data model. Therefore, we would be talking about 
finishing the data model and the event package, both of which should be 
easy to complete given that we may be removing the most controversial 
stuff from the data model (e.g., policies and most complicated media 
usages).

Cheers,

Gonzalo

---

From: Srivatsa Srinivasan <[email-masked]>
Date: Tue, 13 Mar 2007 07:59:01 -0700

Gonzalo,

Okay. I was referring to the media usages in relation to
SDP covered in draft-srinivasan-xcon-usecases-mediausage-01.

Not sure what you mean by the most complicated media usages
-- we decided to leave only the base controls in there, if I
remember right?

Thanks,
Srivatsa.

________________________________________
From: Gonzalo Camarillo [[email-masked]]
Sent: Tuesday, March 13, 2007 4:16 AM
To: Srivatsa Srinivasan
Cc: Henning Schulzrinne; XCON
Subject: Re: [XCON] Policies in the data model

Hi,

Cheers,

Gonzalo