The primary purpose of the Catalog is to associate resources in the document with local system identifiers. The system identifiers returned by the resolution methods in this class are valid, i.e. usable by, and in fact constructed by, the java.net.URL class. Unfortunately, this class seems to behave in somewhat non-standard ways and the system identifiers returned may not be directly usable in a browser or filesystem context. An included catalog occurs logically at the end of the including catalog. The delegated catalogs are not loaded until they are needed, but they are cached once loaded.
Initial behavior is set by the system property xml.catalog.override .
The default initial behavior is 'YES', that is, entries in the catalog override system identifiers specified in the document. If provided with an SAX Parser class, this object can also load XML Catalogs. For the details about which XML Catalog formats are recognized, see XMLCatalogReader . A value of 0 is assumed if the property is not set or is not a number. A value of true is assumed if the property is not set.