Sorry, I just have this bias against designs which conflict with reality. Anyway, it should be extremely easy to create the Java classes described by your original post. So why don't you give that a try and let us know what problems you run into?
As for generating RDF from a collection of those objects, that's a separate problem. In fact Apache has built a whole package to do that sort of thing -- you might want to start by looking that up to get some ideas.
Found it. Based on file dates, it seems I worked on this in 2010. Can't believe it's been 10 years since then. My dabbling was based on https://www.wiley.com/en-us/Semantic+Web+Programming-p-9780470418017. The web site has example code for the book; check out the "HelloSemanticWeb" example in chapter 2. That got me started. I'm attaching the source code for that example.