Possible Catalog Issues for DocBook 4/5: Missing 'www' in System Identifier?

Hi,

not sure if this can be considered as a "bug", but I've stumpled over an
entry in the catalog files, both for DocBook 4 and 5. Maybe someone can
clarify it.

For a long time, the DocBook schema has got two official _system_(!)
identifiers: the one from OASIS and the docbook.org domain. That's the
reason why you can find in the DocBook 4.5 catalog file[1] two entries
to access the DocBook 4.5 DTD:

  <system systemId="http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
          uri="docbookx.dtd"/>
  <system systemId="http://docbook.org/xml/4.5/docbookx.dtd"
          uri="docbookx.dtd"/>

Well, I had always the (wrong?) impression, that the system identifier
for the docbook.org domain contains a "www". Using a Web browser to
access the URL is usually not a problem (as both URLs work, with and
without "www"). However, an XML catalog resolver wants the *exact*
string. If someone tries to use such a system identifier, he will get
into problems.

For example, oXygen 15 creates a DocBook file which contains the "www".
However, they also use the above catalog file. I guess, this problem
hasn't occured yet as all the XML tools try to find the public
identifier first. Assuming there is a correct entry in the XML catalog,
the system identifier never gets resolved (and doesn't need to).

Is this ambiguous? I would say yes. Or at least confusing. 

What would the experts recommend here?

Thanks!

---- Reference
[1] http://www.docbook.org/xml/4.5/catalog.xml

-- 
Gruß/Regards,
    Thomas Schraitle