I posted this today on my blog, because folks were asking about this 
mysterious RWO thing. This is my take on a simple perspective we could 
use. All open for discussion, of course, and no, this is hardly 
exhaustive, just a conversation starter.


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.

Karen Coyle
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