[XML-SIG] What does: Expected type or alternative list mean?

[Remy C. Cool]

When I validate my xml file with xmlproc ... I get the error:
xpdf.xml:2:34: Expected type or alternative list

My xml file starts like this:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE xpdf SYSTEM "xpdf.dtd">
<xpdf>
  <template>
	...

According to the parser, the error should be in the <!DOCTYPE 
definition. Pointers, solutions or clues appreciated.

Regards,
Remy Cool