Remember that the XSD version of the DocBook 5 schema is not normative. It does
its best, but it can't convey all the subtleties of the RELAX NG schema, and
the RNG schema is the only one that's normative.
My hazy understanding is that <phrase> has two lives in DB 5. In its day job,
<phrase> is a taxpaying citizen whose full name is db.phrase, and it has rights
and responsibilities. But there is another <phrase> who goes by db._phrase, and
this is the wild one who goes out at night with a shadowy underground group
that call themselves the nearly ubiquitous inlines.
When the RNG schema allows:
<phrase>
<optional>blue</optional>
</phrase>
it is acknowledging <db.phrase> as a full citizen, and <optional> as a full
citizen member of the Technical Inlines group. Everything's on the up and up.
But when the RNG schema allows:
<optional>
<phrase>red</phrase>
</optional>
it is only because <db._phrase> showed a fake ID at the door, and pretended to
be ubiquitous. And in this context, it is ubiquitous enough.
However, when you (ahem) relax your standards and go all whatever on us, you
start trying out such wildnesses as:
<optional>
<phrase>
<optional>Our goal is world domination</optional>
</phrase>
</optional>
Well now. That's when the RNG schema puts it badge back on and starts checking
IDs and taking names. In the ensuing round-up, it discovers that <db._phrase>
isn't all that ubiquitous and isn't always allowed in the <optional> door -
especially not carrying that <optional> suitcase. Wait, is that suitcase
ticking?
Don't you wish you'd taken that blue pill now?
[Late night silliness aside, I would love to read an accurate and somewhat
saner description of why some ubiquitous inlines aren't always ubiquitous. The
phrase "ubiquitous inlines" is dropped onto the page without definition or
comment in the DB 5 TDG, and it is clearly a source of confusion. And yes, I
did actually buy paper, PDF, and Kindle versions of the book from O'Reilly.]
From: Tim Arnold [mailto:[email protected]]
Sent: Tuesday, October 12, 2010 3:33 PM
To: [email protected]
Subject: [docbook] invalid doc, but why?
Hi,
I have the following V5.0 docbook document and any validator tells me that the
inner <optional> element is invalid. But where does that info come from? All I
can see from the xsd file is that a <phrase> is legal inside an <optional> and
an <optional> is legal inside a <phrase>.
Not questioning the validity, just trying to figure out where the rule is
located.
thanks,
--Tim Arnold
<chapter xmlns="http://docbook.org/ns/docbook";
xml:id="test" version="5.0">
<info><title>my title</title></info>
<section>
<info><title>my section</title></info>
<para>
<optional><phrase><optional>maybe</optional></phrase>
</optional>
</para>
</section>
</chapter>
