Configuring the OASIS catalog

Reference to the DTD is required to validate XML files. The catalog file identifies the DTD and where it can be found by any component of the system.

XML files reference a DTD using:
SYSTEM identifier
A system identifier references the DTD directly on your local file system or on a network location.
<!DOCTYPE concept SYSTEM "C:\MyDTDs\concept.dtd">

The problem with the SYSTEM identifier is that the DTD may be in a different location on another system. This problem can easily appear if you share or exchange XML files with others. To solve this problem, you can use a PUBLIC identifier to reference the DTD.

PUBLIC identifier
A public identifier is an indirect way to reference the DTD.
<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "C:\MyDTDs\concept.dtd">

If a PUBLIC identifier is used, the catalog file is referenced to locate the DTD. Only when no matching entry for that PUBLIC identifier can be found in the catalog file, the SYSTEM identifier is used.

The catalog files used by Content Manager

The catalog files are located on the server. There are 2 types of catalog files in use:
  1. An XML catalog is used by Content Manager: $\Web\Author\ASP\DocTypes\catalog.xml. For an out-of-the-box DITA installation, this catalog file includes another catalog file, catalog-dita.xml.
  2. A text catalog is used by the XML editors: $\Web\Author\ASP\DocTypes\catalog.

Example

If you want to declare a new DITA specialization with the following PUBLIC identifier "-//SDL XYSOFT//DTD DITA Function//EN", you must update the catalog-dita.xml file. In the uri attribute, the location to the DTD should be defined relative to the location of the catalog file. This must be repeated for all files that the DTD is referencing. In the example below, the DTD function.dtd also references the files function.mod and dialectDomain.ent.In a similar way, although the syntax differs slightly, you also must update the file catalog.

More information

It is worth noting that Content Manager supports the full OASIS catalog specification (the prefer attribute is not supported).

For more details, refer to http://www.oasis-open.org/committees/entity/spec-2001-08-06.html.