Fwd: The need for RDF in Linked Data

[Followup to semantic-web@w3.org please]

-------- Original Message --------
Subject: The need for RDF in Linked Data
Date: Mon, 17 Jun 2013 01:26:35 -0400
From: David Booth <david@dbooth.org>
CC: semantic-web <semantic-web@w3.org>

There seems to be some persistent misunderstanding about the
role of RDF in Linked Data, as evidenced by comments like
the following:

   "RDF is just one implementation of Linked Data"

If Linked Data is intended to support the goal of the Semantic
Web, then unless the Semantic Web is re-architected with a new
foundation, RDF is *essential* to Linked Data -- not optional,
and not merely one potential choice among many.  the reason is
that the Semantic Web critically relies on the use of *both*
a standard universal identification convention (URIs) for its
vocabulary, *and* a standard universal information model (RDF)
for making statements.

To understand why a standard universal information model
is important, one must think back to the central goal
of the Semantic Web.  the goal is to enable computers
to do more useful things for us: to enable them to
find, share, combine and make meaningful use of web data.
This means that a client application processing some web data
should be able to follow links in that data to find more data
that it can *also* meaningfully use.  the only way that can be
achieved is by using a standard universal information model.
otherwise the client application will have no reliable way to
properly interpret that new data.

For example, suppose the client application dereferences
a URI and obtains a comma-separated-values (CSV) document.
unless the client application knew how to interpret that file,
it would not be able to make meaningful use of that data.
it would be stuck at a dead end.  but if the document were
expressed in a standard universal information model, then
the client application would at least be able to understand
what statements the document was making.  and if the client
application did not already understand the vocabulary --
i.e. the meanings of the URIs -- then it could recursively,
using Linked Data techniques, dereference the URIs to discover
their meanings.

Why does RDF need to be the standard universal information
model?  not because it is perfect, but because *some* standard
universal information model is needed, and that is the one
that was chosen, just as URIs were chosen to be the standard
universal identification convention.  furthermore, because RDF
is syntax independent, a document does not have to *look* like
RDF in order to be interpreted as RDF. for example, GRDDL allows
arbitrary XML to be interpreted as RDF.  The enormous value
of JSON-LD is that it provides a more web-developer-friendly
syntax than ever before for a universal information model.

why couldn't other sufficiently powerful information models
achieve the same Semantic Web goal just as well, and be used
in addition to RDF?  Because that would fragment the web.
instead of one web we would have many webs, each one its own
walled garden, and that is not be Semantic Web goal.  without a
shared information model, client applications would not be
able to meaningfully combine the data from those walled gardens.

I do not expect anyone to take my word for this. All I ask is
that you think about it.  Because if you do, the conclusion
is unavoidable: if Linked Data is going to support the goal
of the Semantic Web (without re-architecting it), then Linked
Data MUST be based on RDF.

this obviously begs the question: *should* Linked Data support
the goal of the Semantic Web?  that certainly was TimBL's
intent when he coined the term and wrote his article about
it: http://www.w3.org/DesignIssues/LinkedData.html (but I
continue to be amazed at how differently different people seem
to understand that article, so I imagine there would still be
some who would disagree even with *that* point.)

*I* certainly think that Linked Data should support the goal
of the Semantic Web.  and I think that JSON-LD -- *because*
it will be such a web-developer-friendly RDF syntax (assuming
a few small issues are resolved, so that it really *is* an
RDF syntax) -- will be a big step forward.

If the term Linked Data is "hijacked" by a broader population
to mean *any* sort of data that is linked -- not necessarily
RDF -- then this will be a major loss to the Semantic Web
community, because it is very hard to come up with simple ways
to communicate the essence of the Semantic Web.  The Linked
Data meme has been extremely helpful.  If the RDF component
is lost, we will have lost the best meme we have ever had for
explaining the Semantic Web.`


[Followup to semantic-web@w3.org please]

Received on Monday, 17 June 2013 05:34:43 UTC