Let's take the following OASIS catalog TestXMLCatalog.xml :
Add it to netbeans catalog with Tools> DTD and XML schemas then "add Catalog"
and selecting "Oasis catalog resolver" an browsing to the file above (TestXMLCatalog.xml).
As a result a new node appears as "Resolver at TestXMLCatalog.xml" but it has no child.
Add the following line to TestXMLCatalog.xml
<public publicId="Schema public Id"
add anew the modified catalog, in the catalog view the node "Resolver at TestXMLCatalog.xml" has only one child : the one corresponding to the public entry.
Sounds like a bug - not sure if this ever worked. I don't think this is considered a primary IDE feature, lowering priority to P3.
Just to confirm - what is the main reason for adding the catalog to the registry? To provide code completion based on the schema? That should normally work even without adding a catalog.
A catalog is very handy when you work with no internet access.
You can manage to avoid validating processes (e.g. in a build step of a build suite) to fail when facing network failures.
Please note that Netbeans off the self catalogs are not comprehensive.
Report from old NetBeans version. Due to code changes since it was reported likely not reproducible now. Feel free to reopen if happens in 8.0.2 or 8.1.