XMLSpy supports a subset of the OASIS XML catalogs mechanism. The catalog mechanism enables XMLSpy to retrieve commonly used schemas (as well as stylesheets and other files) from local user folders. This increases the overall processing speed, enables users to work offline (that is, not connected to a network), and improves the portability of documents (because URIs would then need to be changed only in the catalog files.)
The catalog mechanism in XMLSpy works as outlined in this section:
For more information on catalogs, see the XML Catalogs specification.