The catalog files used by Content Manager
The catalog files are located on the server. 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.
It is worth noting that Content Manager supports the OASIS catalog specification.
For more details, refer to http://www.oasis-open.org/committees/entity/spec-2001-08-06.html.