[It would be nice to provide a more recent docbook as a package enhancement too.] By unaware, I mean that sgmlcheck, sgml2x do not seem to know that the sgml library is in /usr/lib/sgml. Indeed, sgmltools have their own dtd directory, /usr/lib/sgml-tools/dtd. I suspect at Redhat people do not use these particular versions of docbook, sgml-common and sgml-tools. If so, it would be nice to provide those working versions. To reproduce the problem (or prove me wrong:-), just try sgmlcheck docbooksgmlfile Thanks.
sgml-tools only works for LinuxDoc and HTML I'm afraid. You can use openjade and programs like 'db2html' (from the stylesheets package) to process DocBook documents. The documentation probably needs updating to say something to that effect..
*** This bug has been marked as a duplicate of 18858 ***