Subject: [Simple] Minutes from the XML schema

From: Aki Niemi <[email-masked]>
Date: Tue, 08 Mar 2005 22:29:17 +0200

All,

Here are my minutes from the workshop held at the end of today's SIMPLE 
meeting. Please send comments and corrections my way.

Cheers,
Aki

---

SIMPLE Schema design working session minutes
============================================

Slides are at:
http://www.softarmor.com/simple/meets/ietf62/slides/simple62-schema-design.ppt

Roster:
Jonathan Rosenberg (chair)
Cullen Jennings
Scott Hollenbeck
Hannes Tschofenig
Henning Schultzrinne
Jari Urpalainen
AC Mahendran
Aki Niemi (sec)
Viay Gurbani
Rohan Mahy
Hisham Khartabil

Various documents are doing schema design in different ways. Objective
is to unify and also reduce the amount of namespace declarations in
the XML instance documents.

* Can we have a single namespace for all of the extensions? GML seesm to
   be doing this, so yes. Although it is gludgy, since the schema
   location is optional.

* If you use the original PIDF schema, then you can't validate the
   extensions using that namespace.

* Preference is to use a single namespace. There are anyway probably not
   going to be colliding element names.

* One namespace and multiple schemas is not a clean
   architecture. There are also cases where a document is validated
   using a schema that is not based on namespace declarations, but is
   from other source. I.e., you just *know* against which schema to
   validate the document.

* Namespace declarations seem not important. The application will
   anyway validate against the schema it knows of. It doesn't matter if
   the document has half dozen other declarations that the validator does
   not know.

Extensibility discussion
------------------------

* There is a fundamental design decision to make: whether we extend
   using substitution groups and any declarations.

* Jari is arguing for a hybrid model, where abstract element
   definition and any declaration is used, so that if the application has
   the schema, it will validate, but if it doesn't, it will fall back to
   <any> -- seems to solve part of the problem, but not all of it.

* Requirement is: for an extension, if you have the schema, validate
   it; if you don't let it pass.

* Element substitution seems a lot better than type substitution. Data
   model is currently doing type substitution -- but that is now gone
   anyway.

* Requirement is also: an application only looks into places where it
   knows to look for things.

Proposals:

* Proposal is to go with the any declaration only. I.e., the
   validation is not that important when applications are in any case
   going to validate against PIDF, which has the any declaration with
   processContents="lax" only.

Namespace issue: desire to make instance documents smaller
----------------------------------------------------------

* About colliding names: this actually happens and colliding names are
   possible even within the same working group

* Data model could import the pidf namespace, RPID, CIPID, prescaps,
   etc. This would still have multiple namespace declarations, but
   reduce the number in any case.

Proposals:

* Proposal: PIDF uses its own namespace; Data model, RPID, CIPID, and
   future extend the above and share a single namespace; and prescaps
   has its own namespace

* Proposal: there will be a schema design team that will share the
   schemas and coordinate the work. Henning proposes to have the schemas
   in a single location. Use CVS: whenever something gets added into the
   CVS, the whole lot has to "compile". Jari and Henning will work
   together and come up with the tools to do this.

* Proposed action item: tutorial and sinple examples need to be
   constructed to get input and review from the community. Owner unknown.

* This same discussion should apply to GEOPRIV.

EOF

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From: Jaekwon Oh <[email-masked]>
Date: Wed, 09 Mar 2005 18:07:37 +0900

Hello All,

According to the XFont's Best Practise that has been referred in the slides, it is also recommended to design a schema swichable between namespace exposition and localization and, in order to achieve this, to minimize the use of global elements and attributes.
The Venetian Blind Design Model looks good to be adopted for this purpose.
As noted in the Best Practises, localized names would improve readability and simplicity with some bandwidth gain, which is valuable especially in wireless media.

BR,
Jaekwon

=====================================
Jaekwon Oh

System Engineer
Global Standards & Strategy Team
Telecommunication R&D Center
Samsung Electronics Co., Ltd.

Tel +82-31-279-5086
Fax +82-31-279-5130
CP +82-16-9530-5086
[email-masked]
=====================================

---

From: Hisham Khartabil <[email-masked]>
Date: Wed, 9 Mar 2005 16:45:28 +0100

What worries me about this work is that it will most certainly delay  
our progress. If people really strongly feel that this work needs to be  
done, then lets prioritise this work and expedite the output of this  
exercise.

I would suggest a design team that is committed to producing results  
fast (preferably within a month). Good candidates for the design team  
would be the people listed below. If you would like to be included in  
the design team, please drop me an email, but please keep in mind that  
we want contributors and not listeners.

Regards,
Hisham

On Mar 8, 2005, at 9:29 PM, Aki Niemi wrote:

> All,
>
> Here are my minutes from the workshop held at the end of today's  
> SIMPLE meeting. Please send comments and corrections my way.
>
> Cheers,
> Aki
>
> ---
>

---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 09 Mar 2005 15:12:17 -0500

We currently have schemas that don't compile and have broken 
extensibility mechanisms. This needs to be fixed for us to make 
progress. I don't know how you could argue that this will just delay us.

I do agree with trying to deliver something in a timeframe. I think a 
month is reasonable. I would suggest that, within a month, we have the 
following in place:

1. all of our xml-related documents resubmitted with updated schema 
compliant to our guidelines

2. a small I-D that is published defining the design guidelines in a way 
that non-simple yet xml-experts can read and comment on

3. an automated process for validating all of the schemas and a check 
against examples

Does this sound reasonable?

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com