Proposed Response to FPDAM Part 1 BR-0001, et al

Alex Brown alexb at
Thu Feb 4 16:35:18 CET 2010

Shawn, all,

I think versioning and extensibility _can be_ intertwined, but that's a particular approach and whether it applies to 29500 depends to a large extent on how the S/T discussions are concluded. One view might be that OOXML is "versioned" through standardizing extensions; another is that the core schemas themselves are versioned and extensions remain a discrete class of thing, inside or outside the standard. We haven't decided which of these (or other) approaches to take yet.

Some topics (like versioning of extensions) we haven't yet touched yet, so far as I can remember.

It's probably not fruitful to discuss the i4i thing here (or in the disposition), but if we imagine that - for valid or invalid reasons - it is decided that CustomXML has to come out of the Standard, then we will be faced with exactly the kind of versioning problem that a version-via-extension technique would not cater for very well.

I'm certainly not against taking strong positions where we have them: but my impression is that WG 4 doesn't have a strong position here. I believe we have solved some immediate problems with this amendment, and that we have answered the Swiss comment - but  I don't believe we yet have a good story to tell about versioning and extensions in all respects - and so I don't want us to say that we have.

Or is it just me?

- Alex.

From: Shawn Villaron [mailto:shawnv at]
Sent: 04 February 2010 14:16
To: Alex Brown; e-SC34-WG4 at
Subject: RE: Proposed Response to FPDAM Part 1 BR-0001, et al

I would assert that versioning and extensibility are inherently intertwined and hence I think it's important to educate the various groups what technical tools we have at our disposal.  I'm not sure that that ties our hands in any way - it just says that, as of today, these are the tools in our toolbox and our understand of how we'd use them.  It doesn't say that we can't acquire more tools or find new uses for the existing tools.  It's merely an observation at a point in time.  I really don't think that this restricts us at all.

The CustomXML comment is a complete red herring ... i4i doesn't apply at all to this standard and hence there is no reason that we should be considering removing it.

I'm still baffled why we're afraid to take a position here.  We're willing to take lots of strong positions elsewhere.  Why are we scared when it comes to "versioning?"

From: Alex Brown [mailto:alexb at]
Sent: Thursday, February 04, 2010 2:15 AM
To: e-SC34-WG4 at
Subject: RE: Proposed Response to FPDAM Part 1 BR-0001, et al

Dear all,

This is not quite right as a response, I think.

First, WG 4 has not "concluded" that we should not add versioning to 29500. My recollection is that in Prague we decided to park that discussion and focus on the immediate issues raised by the Swiss comments. I think it would be more accurate to state that this topic is still being studied in WG 4.

Secondly, I'm not sure it's a good idea to list technologies that we use for versioning, either - partly because this risks confusing versioning technology with extensibility mechanisms, and partly because it might be seen to bind us to a certain approach. Stating that we are using Namespaces (a very blunt instrument) for our major changes is potentially a hostage to fortune.

Of course it _may_ be that we conclude not to add any (more) versioning mechanisms to OOXML.

However, I think it is also likely that we may want to add rich semantics to help consumers know precisely what it is they are consuming - this includes version information but is not limited to it: we may wish to convey information about the status and version of extensions being included, for example.

And if we decide to make first-class changes to the schemas, I believe we may need a versioning mechanisms then. So if (as seems likely) there is a move to amend 29500 to remove CustomXML, how will we convey to consumers that they are consuming resources that conform to this amended spec? We're not going to make another global Namespace change are we?

Until we have thoroughly explored these kinds of issues, I propose responding as follows:

"WG 4 is still studying the topic of versioning in general, and BR is encouraged to participate in those discussions. The current amendment is focused on addressing the particular versioning issue raised  CH, and does not preclude further work in this area."

- Alex.

From: Shawn Villaron [mailto:shawnv at]
Sent: 22 January 2010 21:56
To: SC 34 WG4
Subject: Proposed Response to FPDAM Part 1 BR-0001, et al

Good afternoon,

Here is my proposed draft response for this series of comments.  Comments welcome, as always.


WG4 Response


WG4 has conducted extensive research into versioning technology associated with ISO/IEC 29500.  Our conclusions are that, absent a clearly specified, unsupported versioning use case, additional versioning technology should not be added to ISO/IEC 29500.  The potential consequences of introducing a flawed versioning technology clearly outweigh any potential benefits.

Furthermore, ISO/IEC 29500 already supports a number of different mechanisms to enable many versioning scenarios.  Here is a sampling of such mechanisms:

*         XML Namespaces - Provides for "major" version increments that are not designed to be backward compatible with existing implementations.

*         Extension Lists - Provides for adding orthogonal data in predefined locations within the XML.  See Part 1.

*         Parts - Provides for adding entirely new payloads into the file container.  See Part 2.

*         Alternative Content Blocks - Provides for adding multiple renditions anywhere in the XML.  See Part 3.

*         Ignorable Namespaces - Provides for adding orthogonal data anywhere in the XML.  See Part 3.

Given these, and other, mechanisms currently provided for in ISO/IEC 29500, and that such mechanisms provide support for the known versioning use cases, WG4 does not believe we need a new versioning technology.  We continue to evaluate new versioning-related use cases, and in the event we find one which cannot be supported by existing versioning technologies, we will consider adding additional versioning technology at that time.

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