Letting components be empty

[Norman Walsh <ndw@nwalsh.com>]

"Bob Stayton" <bobs@sagehill.net> writes:

> 6.  DocBook assembly.
>
> Bob raised RFE 3368297 to allow hierarchical elements to
> be empty except for title.  The expectation is that
> such empty elements would be populated during the
> assembly process.  Basically the content models would
> change from using + to using * for block and sections.
> Since this loosens the content models, the change would
> be backwards compatible.
>
> Proposal to accept 3368297 was approved.

This has some interesting consequences. Right now, the content model
of a component is

  db.navigation.components*, db.toplevel.blocks.or.sections, db.navigation.components*

In other words, there are some navigation components (toc, glossary,
index, etc.) that can occur (optionally) at either the beginning or
the end. Between them there must be at least one block-level element
or section.

The change agreed above makes the middle part effectively:

    (db.all.blocks*, db.toplevel.sections*)

Which means you can have blocks (optionally) before the first section
then (optionally) any number of sections.

That makes the component content model:

   db.navigation.components*, db.all.blocks*, db.toplevel.sections*, db.navigation.components*

which is, I believe, ambiguous in XSD. It's certainly not valid in a
DTD.

That suggests that to make an XSD or DTD, we'll wind up with

  (db.navigation.components | db.all.blocks | db.toplevel.sections)*

which is...just so bad. One more reason why y'all ought to be
pressuring your tool vendors for RELAX NG support!

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com>      | There is always some accident in
http://www.oasis-open.org/docbook/ | the best of things, whether
Chair, DocBook Technical Committee | thoughts or expressions or deeds.
                                   | The memorable thought, the happy
                                   | expression, the admirable deed are
                                   | only partly yours.--Henry David
                                   | Thoreau

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