db.cals.table problem in "PTO" (bug?)

[Dalan Hurst <d@webbscreek.us>]

The following example seems to be correct, at least as I understand the
Definitive Guide:

<article xmlns="http://docbook.org/ns/docbook";>
  <info><title>Test</title></info>
  <table>
    <title>db.cals.table</title>
    <tgroup cols="2">
      <colspec colname="c1" />
      <colspec colname="c2" />
      <thead>
        <row>
          <entry namest="c1" nameend="c2">Both columns.</entry>
        </row>
      </thead>
      <tbody>
        <row>
          <entry namest="c1" nameend="c2">Both columns, MkII.</entry>
        </row>
        <row>
          <entry>1st column</entry>
          <entry>2nd column</entry>
        </row>
        <row>
          <entry namest="c1" nameend="c2">Both columns again.</entry>
        </row>
      </tbody>
    </tgroup>
  </table>
</article>

But it won't validate against docbook.rng.  If i comment out the rows which
contain cells that span, it validates, output of xmllint:

$ xmllint --noout --relaxng ../docbook/rng/docbook.rng table-test.xml
table-test.xml:10: element entry: Relax-NG validity error : Invalid attribute
namest for element entry
table-test.xml:5: element tgroup: Relax-NG validity error : Element tgroup
failed to validate content
table-test.xml:4: element title: Relax-NG validity error : Expecting element
caption, got title
table-test.xml:4: element title: Relax-NG validity error : Element table failed
to validate content
table-test.xml:3: element table: Relax-NG validity error : Expecting element
informalexample, got table
table-test.xml:3: element table: Relax-NG validity error : Element article
failed to validate content
table-test.xml fails to validate

If this is a bug, I will be happy to file a report.

Cheers,
d