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Subject: RE: [dita] W3C XML Schema 1.1

Scott, this quotation is a case where I simply did not catch all the older
documentation when Eric provided the new design pattern for Schemas in
dita132. Thanks for pointing it out.  I will update the doc per Eric's
description--he has the latest word at all times on the state of the

When Eric talks about a revamp of DITA for XSD 1.1, he means a change in
the design pattern for specialization, not in the content models, proper.
Your topic instances should validate the same under either Schema version,
regardless of which design pattern for specialization is used.

Don Day <dond@us.ibm.com>
Chair, OASIS DITA Technical Committee
IBM Lead DITA Architect
11501 Burnet Rd., MS 9037D018, Austin TX 78758
Ph. 512-838-8550   (T/L 678-8550)

"Where is the wisdom we have lost in knowledge?
Where is the knowledge we have lost in information?"
        --T.S. Eliot

             "Tsao, Scott"                                             
             g.com>                                                     To
                                       "Eric Sirois" <esirois@ca.ibm.com>
             04/29/2005 07:46                                           cc
             PM                        <dita@lists.oasis-open.org> 
                                       RE: [dita] W3C XML Schema 1.1 


Thanks for the prompt response.  In the DITA Open Toolkit 1.0.1 readme we
found the following statement regarding the DITA XSD implementation:

            This document describes the release notes and usage of the
            experimental DITA XML Schema on developerWorks®.

            This DITA release includes an implementation of the topic
            architecture in XML Schema. The DTDs are still the canonical
            representation of DITA. The design pattern for the DITA Schemas
            is based on the W3C XML Schema 1.0 Specification and may be
            subject to change in the future.

            The specialization process and design pattern for the DITA XML
            Schema are still being developed and refined. As such, the
            specialization process stated below should not interpreted as
            "the definitive process", but simply one method to specialize
            information types and domains

However, what I understand from your response, DITA does not depend on the
inheritance model of XSD today, and may not in the future either. As such,
our implementation of DITA XSD can go ahead without relying on future
evolution of the XSD standardization process.

Nevertheless, if future release of DITA does incorporate future XSD
enhancements on the inheritance model, we will need to do migration if we
want to adopt such future releases.  Could you please give us a sense how
much a migration effort will that be?



-----Original Message-----
From: Eric Sirois [mailto:esirois@ca.ibm.com]
Sent: Friday, April 29, 2005 8:07 AM
To: Tsao, Scott
Cc: dita@lists.oasis-open.org
Subject: RE: [dita] W3C XML Schema 1.1

Hi Scott,

The current incarnation of the DITA Schemas fully adheres to the XSD 1.0
spec and has no dependency of the XSD 1.1.  The schemas were redesigned
from top to bottom in the developerWorks 1.3.2 to remove any architectural
dependency that would only appear  in XSD 1.1.  Otherwise, most
commercial/open-source XML tools would not be able to validate instance
documents using the DITA Schemas.

If DITA needs requirements for XSD 1.1 (RQ-11) , that would mean that the
DITA Schema would  make use of the XSD inheritance mechanism. Which also
means that the DITA would have to be redesigned from top to bottom. That
does not necessarily mean that DITA will use that feature.

RQ-11 is only an issue *if and only if* we make use the XSD inheritance
model. This is a very important point. If DITA is implemented using the
inheritance model XSD still would not be able to fully implement DITA.
What's missing in the XSD inheritance architecture to fully support the
DITA architecture? Renaming or aliasing element in a specific content model
(local element substitution).  XSD only supports global element
substitution via substitutionGroups.

There is a possibly a way that we may be able to achieve local element
substitution via the XSD inheritance model, but implementing it in XSD
architecture would be very ugly!

We can model the DITA 1.0 and 1.1 using XSD 1.0.  We currently have no
dependency on any XSD 1.1 features.  We may have a dependency on XSD 1.1
features for DITA 2.0, but it will probably not involve any feature that is
dependent on the XSD inheritance architecture.

I hope this helps address your concerns.

Kind regards,

I've included below a response to question regarding *issues* with the DITA
Schemas on the dita-users list (just in case some folks on the TC may not
be subscribe to that list).


There are no issues, per se, with the DITA Schemas. The schemas are fully
equivalent to the DTDs and work fine with most XML authoring
editors...IDE's are another issue.  :-) . The *issue* with the W3C Schemas
is that we are able to take full advantage of the inheritance capabilities.
Why do we want to use the W3C XML Schema inheritance capabilities? Well
because their inheritance rules are pretty close to the DITA inheritance
rules. And if were to make use of that it would be easier for developers to
create valid specializations that conform to the DITA spec.

We developed schemas over a year ago that *tried* Schema inheritance, but
kept hitting wall after wall of issue in the manner some parsers adhered to
the XML Schema 1.0. Some were very strict while other were lax. We could
not get a consistent story. Since the developerWorks DITA 1.3.2 version and
the spec version that is available at OASIS we have removed all use of
inheritance in the schema, but also need to come up with an architecture
that was *fairly easy* to use so developers/authors/architects could create
new specializations. Unfortunately, they still (along with the DTDs...and
same would occur with RNG) manually verify that the specialized element's
content is valid as per the DITA spec.

Probably one of the biggest reason that people are still using the DTDs is
that XSLT 1.0 processors only support DTDs out-of-the-box. Web browsers
only supports DTD parsing. If you look at a schema validate instance in a
browser and trying to use a stylesheet to view the doc...you not going to
see what you were expecting. If you want to see a schema validated instance
doc in a browser you have to use CSS. There are no free XSLT 2.0 (Schema
aware) processor available at this time. You have to pay for Saxonica-SA
and the XMLSpy one. I believe Stylus Studio use Saxonica.

The entire DITA processing system is dependent on a default class attribute
value that appears on every element in DITA, like <xs:attribute ref="class"
default="- topic/topic "/>. All instance docs need to validated so that the
class attributes are normalized...then and only then can the instance
document be processed by the XSL stylesheets.

If your asking yourself...how do I process my instance documents if they
are all schema validated? Well..in the demo directory in the DITA open
source project there is a java directory...in it you will find a couple of
small applications, TransformUsingXMLSchema and ValidateXMLDoc, that can
help those using XML Schemas or want to use XML Schemas to process their

TransformUsingXMLSchema does what the applications says..it can transform
XML Schema validate docs using XSLT 1.0 processors. All the application
does is validate and normalize the class attribute and then pass the doc to
XSLT processor to be processed.

ValidateXMLDoc allows you to validate an XML instance doc with an external
schema when the instance has a DOCTYPE defined in it. You don't need to
modify your multitude of legacy docs that have the DOCTYPE in it for them
to be validated. Unfortunately, this option is implemented in
TransformUsingXMLSchema yet. If someone has a requirement or would like to
see the feature added to it...let us know or open a feature request on

I hope this helps clear up some of the *issues* regarding XML Schemas...or
create new ones.  ;-) </snip> Eric A. Sirois Staff Software Developer DB2
Universal Database - DBA XML Tools Development IBM Canada Ltd. - Toronto
Software Lab
Email: esirois@ca.ibm.com
Phone:(905) 413-2841
Blue Pages (Internal)

"Transparency and accessibility requirements dictate that public
information and government transactions avoid depending on technologies
that imply or impose a specific product or platform on businesses or
citizens" - EU on XML-based office document formats.

             "Tsao, Scott"
             g.com>                                                     To
                                       Eric Sirois/Toronto/IBM@IBMCA
             04/28/2005 06:35                                           cc
             PM                        <dita@lists.oasis-open.org>
                                       RE: [dita] W3C XML Schema 1.1


Thanks for the reply.  I noticed that this feature has been included in the
XML Schema 1.1 requirements (see
http://www.w3.org/TR/xmlschema-11-req/#N40014F).  However, since we are
using the W3C XML Schema 1.0 spec (not DTD) for most (if not all) of our
XML projects at Boeing, I am concerned if we are taking a major risk to
adopt DITA today before the following events actually happen:
1) W3C releases the XML Schema 1.1 Recommendation
2) DITA incorporates the needed feature(s) of XML Schema 1.1

Please help us better understand the potential risks.



-----Original Message-----
From: Eric Sirois [mailto:esirois@ca.ibm.com]
Sent: Monday, September 20, 2004 11:10 AM
To: Tsao, Scott
Cc: dita@lists.oasis-open.org
Subject: Re: [dita] W3C XML Schema 1.1

Hi Scott,

The issue related to "restriction via subsumption" is still active within
the XML Schema WG.

RQ-17 -
 (not sure if you have to be a W3C member to view the document).

I did speak to IBM's rep on the workgroup and he's is aware of our
requirements as well as the WG. They working on solving this issue for WXS
1.1. Part of the new algorithm is implemented in Saxon 8.0 and XSV

Kind regards,
Eric A. Sirois
Staff Software Developer
DB2 Universal Database - DBA XML Tools Development
IBM Canada Ltd. - Toronto Software Lab
Email: esirois@ca.ibm.com
Phone:(905) 413-2841
Blue Pages (Internal)

             "Tsao, Scott"



             09/15/2004 02:09

                                       [dita] W3C XML Schema 1.1

I recall that someone has mentioned that DITA requires functionality beyond
the current XML Schema (1.0) spec, and I wonder if those requirements have
been documented somewhere and are being considered by the W3C WG to be
included in the XML Schema 1.1 spec.


Scott Tsao
The Boeing Company
P.O. Box 3707, MC 67-EF
Seattle, WA 98124-2207

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