RDF data are processed silently so there's not much feedback to be had. A few tricks exist.
RDF documents usually contain whitespace that hint at the purpose of the facts stated. You can strip that whitespace out and view such a document as plain, hierarchical XML. To do this, just change the file extension to .xml (or use a shortcut or a link) and load it directly into a Navigator window.
There is no need to restart Mozilla every time you read an RDF document, or even every time you modify that document by hand. The document is managed by the Mozilla cache. If you modify the fact store extensively (and get lost), then you should restart Mozilla entirely.
The RDF diagram (as in Figure 11.5) for a given document ...