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
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
* 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.
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