NVDL, DocBook, and MathML

[Bob Stayton <bobs@sagehill.net>]

I'm having a problem trying to process DocBook 5 documents using NVDL in 
order to validate DocBook content that has MathML content within 
equation or inlineequation.  The DocBook validation side is failing, but 
only under NVDL.

The DocBook rng schema for inlineequation is as follows:

   <define name="db.inlineequation.content">
      <choice>
         <choice>
            <oneOrMore>
               <ref name="db.inlinemediaobject"/>
            </oneOrMore>
            <oneOrMore>
               <ref name="db.mathphrase"/>
            </oneOrMore>
         </choice>
         <oneOrMore>
            <ref name="db._any.mml"/>
         </oneOrMore>
      </choice>
   </define>

This schema specifies either a) inlinemediaobject or mathphrase, or b) 
some MathML elements.  It *allows* MathML, but it does not validate it 
against the MathML DTD.  NVDL is capable of doing that.  But ...

When I set up NVDL using a schema like this:

<rules xmlns="http://purl.oclc.org/dsdl/nvdl/ns/structure/1.0"; 
startMode="docbook">
    <mode name="docbook">
        <namespace ns="http://docbook.org/ns/docbook";>
            <validate schema="docbook.rng"/>
        </namespace>
        <namespace ns="http://www.w3.org/1998/Math/MathML";>
            <validate schema="../xsd/mathml3/mathml3.xsd"/>
        </namespace>
    </mode>
</rules>

This DocBook content validates against docbook.rng:

<para><inlineequation>
  <math xmlns="http://www.w3.org/1998/Math/MathML";>
    ...
  </math>
</inlineequation></para>

But when processed with NVDL, it fails with this message:

Engine name: Jing
Severity: error
Description: element "inlineequation" incomplete; expected element 
"alt", "inlinemediaobject" or "mathphrase" or an element from another 
namespace

I think what is happening is that Jing has sent the <math> element to be 
validated against the MathML schema, and then it sends the remains of 
the inlineequation element to be validated against the DocBook schema. 
But now inlineequation is empty, and fails validation.

I find if I insert an empty <mathphrase> inside inlineequation, then I 
can work around this error.  Does anyone have any other ideas? That is, 
short of customizing the docbook equation elements to allow them to be 
empty.

--
Bob Stayton
Sagehill Enterprises
bobs@sagehill.net