A few tips about using XML catalogs on Cygwin -

  - if you already have the Cygwin "docbook-xsl" and "docbook-xml42"
    packages installed via the Cygwin setup app, you already have a
    catalog at /etc/xml/catalog (those packages install and update it)

  - there's a small problem in the catalog entry that the current
    (v1.65.1) docbook-xsl package installs; the problem is, it has:

      <rewriteSystem systemIdStartString="http://docbook.sourceforge.net/release/xsl/current/" rewritePrefix="/usr/share/docbook-xsl/"/>

    But it should have this:

      <rewriteURI uriStartString="http://docbook.sourceforge.net/release/xsl/current/" rewritePrefix="/usr/share/docbook-xsl/"/>

    You can fix that by running this command:

      xmlcatalog --noout --add rewriteURI \
        http://docbook.sourceforge.net/release/xsl/current/ \
        /usr/share/docbook-xsl/ \
        /etc/xml/catalog

  - once you've made that fix, if you use xsltproc, you don't need to do
    any additional config to enable catalog support for DocBook docs;
    just, if you have "local" URIs like href="/usr/local/share/xsl/..."
    in a stylesheet customization layer or whatever, replace them with
    href="http://docbook.sourceforge.net/release/xsl/current/";

  - if you're using Saxon or another Java-based XSLT engine, your engine
    won't understand the pathnames in your /etc/xml/catalog file --
    because java is a native Windows app, not (yet) complied for
    Cygwin; so there are a few more steps:

      - create a separate "Windows" catalog file; run the following
        commands:

          xmlcatalog --create > /etc/xml/catalog-windows

          xmlcatalog --noout --add rewriteURI \
            http://docbook.sourceforge.net/release/xsl/current/ \
            c:/cygwin/usr/share/docbook-xsl/ \
            /etc/xml/catalog-windows

          xmlcatalog --noout --add rewriteSystem \
            http://www.oasis-open.org/docbook/xml/4.2/ \
            c:/cygwin/usr/share/docbook-xml42/ \
            /etc/xml/catalog-windows

       (if your cygwin root isn't in the default "c:/cygwin" location,
       of course change that bit to whatever matches your Cygwin install)

     - to tell the xml-commons resolver where to find the catalog, you
       need to install a CatalogManager.properties file; do this:

          mkdir -p /etc/java/resolver
          cd /etc/java/resolver
          wget http://xml.apache.org/commons/components/resolver/CatalogManager.properties
          mv CatalogManager.properties CatalogManager.properties.old

          sed 's#^catalogs=.\+$#catalogs=c:/cygwin/etc/xml/catalog#; s#^verbosity=.\+$#verbosity=1#' \
            CatalogManager.properties.old > CatalogManager.properties

       Then you'll need to make sure to add "c:/cygwin/etc/java/resolver/"
       to your Java classpath, either via the CLASSPATH environment
       variable, or the java -cp option (note: the resolver needs the
       *directory* name -- not the CatalogManager.properties filename;
       don't put "c:/cygwin/etc/java/resolver/CatalogManager.properties"

       From there on, just follow the instructions in Bob's book -

         http://sagehill.net/docbookxsl/UseCatalog.html#UsingCatalogsSaxon