basic catalog question

[Craig White <craig@tobyhouse.com>]

Still working through Docbook-XSL 4thEd...

got everything but Xerces working (I'll leave this for another time or
maybe I don't need it) but I have read/re-read/re-read Chapter 5 on
Catalogs and I'm still not confident that I am grasping things.

I'm trying to localize it for my own use...

# cat catalog.dtd
<?xml version="1.0" ?>
<!DOCTYPE catalog
  PUBLIC "-//Toby House/DTD Entity Resolution XML Catalog V.09//EN"
  "http://srv1.tobyhouse.com/docbook/catalog.dtd"; >
<catalog xmlns="tobyhouse:names:tc:entity:xmlns:xml:catalog" >
  <group prefer="public" xml:base="file:///var/www/html/" >
    <public
      publicId="-//Toby House//DTD Docbook XML V4.5//EN"
      uri="docbook45/docbookx.dtd" />
    <system
      systemId="http://srv1.tobyhouse.com/docbook/xml/4.5/docbookx.dtd";
      uri="docbook/docbookx.dtd" />
    <system
      systemId="docbook4.5.dtd"
      uri="docbook45/docbookx.dtd" />
  </group>
</catalog>

Does this make sense?

I can't test it because...

# xmllint --valid catalog.dtd
http://srv1.tobyhouse.com/docbook/catalog.dtd:1: parser error : Missing
encoding in text declaration
<?xml version="1.0" ?>
                    ^
http://srv1.tobyhouse.com/docbook/catalog.dtd:2: parser error : Content
error in the external subset
<!DOCTYPE catalog
^
http://srv1.tobyhouse.com/docbook/catalog.dtd:2: parser error : Content
error in the external subset
<!DOCTYPE catalog
^

and without the space before the question mark, I got error...

http://srv1.tobyhouse.com/docbook/catalog.dtd:1: parser error : Space
needed here
<?xml version="1.0"?>
                   ^
http://srv1.tobyhouse.com/docbook/catalog.dtd:2: parser error : Content
error in the external subset
<!DOCTYPE catalog
^
http://srv1.tobyhouse.com/docbook/catalog.dtd:2: parser error : Content
error in the external subset
<!DOCTYPE catalog
^

I'm confused...