DOCBOOK-APPS: Can't create alt-tag from textobject

[Lars Bj�rndal]

Look at this, please:

<!DOCTYPE Article PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
<Article lang="no">

  <articleinfo>
    <mediaobject>
      <imageobject>
        <imagedata  Fileref="./logo.png" align="center">
      </imageobject>
      <textobject>
        <phrase>Logo</phrase>
      </textobject>
    </mediaobject>
...

While producing html, I can't get the alt-tag. I have also tried to
place this sequence at another location in the document, but it gives the
same result. What can I do to get the alt-tag?

Lars