catalog.xml doctype declaration

Which public ID and system ID should a Debian package maintainer put in
the doctype declaration when writing a new catalog.xml file for a
package?

I found at least two examples in the Debian XML Policy,
http://debian-xml-sgml.alioth.debian.org/xml-policy/xml-catalog-hierarchy.html

<!DOCTYPE catalog PUBLIC "-//OASIS//DTD XML Catalogs V1.0//EN"
          "file:///usr/share/xml/schema/xml-core/catalog.dtd">

<!DOCTYPE catalog PUBLIC "-//OASIS//DTD XML Catalogs V1.0//EN"
  "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd">