>no widespread DTDs beyond validation and perhaps guided authoring.

Which is plenty. A lot of DTD-based systems aren't broke, so they never got fixed. People behind those systems feel pressure to move to XSD, but heard that RNG is better... and then they remember that what they have isn't broke, and the few extra features they'd like would be so much extra trouble that they stay where they are.

The day after St. Patrick's Day, let me use an Irish expression to say that for doing this, you are a friggin' saint, because this work is a key bridge to ease the transition from DTDs to RNG-based systems for a lot of people. DocBook is almost perfect for a lot of shops, and once they add a few customizations to make it perfect they still want the DTD versions of the complete schemas to work with their existing workflows, so this work really will benefit a lot of people.

The process for generating the MathML DTD (and XSD) is similar from the high level view: XSLT to simplify the relaxNG as necessary then convert to final form. One difference was that I continued to use trang for the final step rather than getting the xslt to write out DTD or XSD directly, although I wasn't always sure that was a good idea.

It might be possible to create a DTD that allowed MathML in the appropriate places, but that's more than the minimum needed to declare victory.

Hmph you set your standards so low:-)

Hopefully though all that should be needed is a (empty) parameter entity as an extension point in the content model of the equation element and then extending that to include math from the mathml dtd should be an easy customisation for those that need it?

Hi Norm, I'm very interested in this subject.

We use XMetaL and have tricked it out over the years with all sorts of convenience features. Unfortunately, XMetaL only supports DTDs and XSD. They seem unlikely to add support for RelaxNG (though they did recently add basic support for xinclude).

I've been planning to move to DocBook 5.0 this summer as part of a general update of our tool chain, but hadn't realized that creating DTDs/XSDs from a DocBook 5.0 customization layer was problematic. My customization of DocBook will mainly be to turn certain features off (e.g. html tables) and adding some common attributes.

Some questions:

It wasn't clear to me (in part because I haven't yet worked with a RelaxNG schema) which parts were the manual, human parts v. the parts handled automatically by the pipeline.

Will you make the pipeline and xslts available? (The intention is for people to customize the RelaxNG and then generate a DTD, right? Not recustomize a generated-by-Norm DTD with every new DocBook 5.x release.)

Should I assume from your last sentence that a hand authored xsd 1.1 schema would be the ideal solution? (i.e. that generating an xsd from the RelaxNG would be just as messy as generating a DTD)

Thanks, David

Shame on me. You're absolutely right, David. I'll see if I can tweak things to embed an empty PE at the point where MathML (and elsewhere, SVG) could be inserted.

I generate the DTD directly because I decided not to even try to make the intermediate (or even final) stages valid RNG. The first step actually translates out of RNG into my own ad hoc vocabulary.

Nice work Norm.

I'm curious why the Publishers Subcommittee ranked DTDs high on the list. At my place of employment, a textbook publisher, the introduction of DocBook 5 resulted in a hue and cry for XSD schemas.

I ended up customizing the publishers RNG to work around the numerous UPA issues. Not ideal, but a decent compromise.

The manual human parts are the simplification of complex content models, like choices between two patterns for the same element and attribute co-constraints.

I checked the pipeline and all the stylesheets into the DocBook project at SourceForge last night. They won't actually run until I publish a new version of XML Calabash though. I'll try to get to that this weekend.

If XMetaL supports XSD 1.1, then a hand authored XSD is likely to be better. I don't know how much better because I don't actually have a good sense of how good or bad the mechanically produced version really is.

Bill, I can certainly comment on the Publishers SC decision to provide a DTD:

Back in August, when the Publishers spec was published for Public Review, we received a comment that a DTD should be provided for the sake of better adoption. The only reason is because of tools support.

I feel equally as strongly as Norm about RelaxNG and the 21st century. In fact, I've been bugging the major tools vendors to support RelaxNG for at least 6 years! I bug them at every conference I see them at. The response is always the same: "We don't have any paying customers that are requesting this feature." I guess we need a grassroots effort or pitchforks and torches to get them to add support!

I also want to echo Bob's sentiments that Norm is a saint for taking on this frustrating and monumental effort!

Due to the difficulty to create the DTD and the amount of elapsed time, the SC decided that providing an XSD from the RNG would be an acceptable substitute, so we do have options.

Why is it ever unsafe to turn interleaves into choices? I suppose that by a choice you mean (a|b|c|...)* rather than just (a|b|c|...), which is clearly not equivalent.

Hi Norm,

You may try to retain the documentation annotations for elements and add them back in the generated DTD as documentation comments (as in the DocBook 4 DTD).

Thanks, George

Norm, is your Definitive DocBook 5 book covering the RelaxNG only? if so, will you provide a bit of content about the DTD and how to get it on your O'Reilly page?