15. url() is XML catalog aware

The URI specified using the standard url() pseudo-function may be resolved using XML catalogs.

For example, this feature can be used to customize the DocBook CSS style sheet bundled with XXE:

@import url(docbook-config:css/docbook.css);1
   my customization here


Note that @import "docbook-config:css/docbook.css"; works fine too. That is, in the case of @import, the url() pseudo-function is not strictly necessary for the XML catalogs to be used to resolve the URI.

This works because the XML catalog bundled with XXE, XXE_install_dir/addon/config/catalog.xml, contains the following rule:

<rewriteURI uriStartString="xxe-config:" rewritePrefix="." />