caption in table

How do I use caption in table?
<http://docbook.org/tdg/en/html/table.html> appears to indicate that if
I use caption, I do not need tgroup (and thead and tbody just follow
caption), but when I do that I get

d:\gnu\sp\bin\nsgmls.exe:mop.xml:229:16:E: there is no attribute "align"
d:\gnu\sp\bin\nsgmls.exe:mop.xml:229:24:E: document type does not allow element "caption" here
d:\gnu\sp\bin\nsgmls.exe:mop.xml:242:7:E: document type does not allow element "thead" here
d:\gnu\sp\bin\nsgmls.exe:mop.xml:244:8:E: document type does not allow element "tbody" here

<table id="inherit-struct">
 <caption align="bottom">
  <simpara>Direct superclass ...</simpara>
  <simpara>Each class ... </simpara></caption>
 <thead><row>...</row></thead>
 <tbody>...
...

What's wrong?

--
Sam Steingold (http://www.podval.org/~sds) running w2k
<http://www.camera.org> <http://www.iris.org.il> <http://www.memri.org/>
<http://www.mideasttruth.com/> <http://www.honestreporting.com>
Don't hit a man when he's down -- kick him; it's easier.