XML Catalogs

Introduction#

An XML catalog is made up of entries from one or more catalog entry files. A catalog entry file is an XML file whose document element is catalog and whose content follows the XML catalog DTD defined by OASIS at https://www.oasis-open.org/committees/entity/spec.html. Most of the elements are catalog entries, each of which serves to map an identifier or URL to another location.

Catalog entry to resolve DTD location

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<public 
   publicId="-//OASIS//DTD DocBook XML V4.5//EN"  4
   uri="docbook45/docbookx.dtd"/>

<system
   systemId="https://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"  5
   uri="docbook45/docbookx.dtd"/>

<system
   systemId="docbook4.5.dtd"    6
   uri="docbook45/docbookx.dtd"/>