I was asked a question about the meaning and import of the RDF concept of "Real World Object" (RWO) and didn't give a very good answer off the cuff. I'll try to make up for that here.
The concept of RWO comes out of the artificial intelligence (AI) community. Imagine that you are developing robots and other machines that must operate within the same world that you and I occupy. You have to find a way to "explain," in a machine-operational way, everything in our world: stairs and ramps, chairs and tables, the effect of gravity on a cup when you miss placing it on the table, the stars, love and loyalty (concepts are also objects in this view). The AI folks have actually set a goal to create such descriptions, which they call ontologies, for everything in the world; for every RWO.
You might consider this a conceit, or a folly, but that's the task they have set for themselves.
The original Scientific American article that described the semantic web used as its example intelligent 'bots that would manage your daily calendar and make appointments for you. This was far short of the AI "ontology of everything" but the result that matters to us now is that there have been AI principles baked into the development of RDF, including the concept of the RWO.
RWO isn't as mysterious as it may seem, and I can provide a simple example from our world. The MARC record for a book has the book as its RWO, and most of its data elements "speak" about the book. At the same time, we can say things about the MARC record, such as who originally created it, and who edited it last, and when. The book and the record are different things, different RWO's in an RDF view. That's not controversial, I would assume.
Our difficulties arise because in the past we didn't have a machine-actionable way to distinguish between those two "things": the book and the record. Each MARC record got an identifier, which identified the record. We've never had identifiers for the thing the record describes (although the ISBN sometimes works this way). It has always been safe to assume that the record was about the book, and what identified the book was the information in the record. So we obviously have a real world object, but we didn't give it its own identifier - because humans could read the text of the record and understand what it meant (most of the time or some of the time).
I'm not fully convinced that everything can be reduced to RWO/not-RWO, and so I'm not buying that is the only way to talk about our world and our data. It should be relatively easy, though, without getting into grand philosophical debates, to determine the difference between our metadata and the thing it describes. That "thing it describes" can be fuzzy in terms of the real world, such as when the spirit of Edgar Cayce speaks through a medium and writes a book. I don't want to have to discuss whether the spirit of Edgar Cayce is real or not. We can just say that "whoever authors the book is as real as it gets." So if we forget RWO in the RDF sense and just look sensibly at our data, I'm sure we can come to a practical agreement that allows both the metadata and the real world object to exist.
That doesn't resolve the problem of identifiers, however, and for machine-processing purposes we do need separate identifiers for our descriptions and what we are describing.* That's the problem we need to solve, and while we may go back and forth a bit on the best solution, the problem is tractable without resorting to philosophical confabulations.
* I think that the multi-level bibliographic descriptions like FRBR and BIBFRAME make this a bit more complex, but I haven't finished thinking about that, so will return if I have a clearer idea.