DOCBOOK: errors ... but where

I'm trying to find where these errors are coming from so I've made a
simplest example and can't see what I've got wrong here (and a few hundred
other errors like them).

--- from the output, first errors from this file before several hundred more
---

/usr/local/cmd/bin/openjade:chap1-intro.sgml:6:11:E: start tag for "TITLE"
omitted, but its declaration does not permit this
/usr/local/cmd/bin/openjade:chap1-intro.sgml:6:11:E: no start tag specified
for implied empty element "TITLE"

--- Here's a file brought in as an entity reference from my main file that
supposedly has the errors. ---

<chapter id="intro">
<title>Introduction</title>

<sect1>
<bridgehead>Test</bridgehead>
<para>test</para>
</sect1>

</chapter>

Any help much appreciated.