I don't understand this idea of making an rdf - what value does the rdf provide? Is there a way to view a diff in terminal that makes it faster / more intuitive? I'm genuinely interested to do this or something like it for drives that are slightly out of sync with each other (yes I know, it's dumb but it happened).
RDF is just an easy way to put everything into a graph, since file systems are stored in a hierarchy. You can use neo4j or whichever graph database, it doesn't have to be rdf. From there you can compare hashes that are in one file system but not in another, and do querying for constraints like largest files, folders with the most files, most recent files, etc.
If your file system is slightly out of sync, try out meld for an easy way to diff.