On Jun 30, 2010, at 6:24 PM, Harry Halpin wrote:
On Wed, Jun 30, 2010 at 8:17 PM, Pat Hayes <pha...@ihmc.us> wrote:
On Jun 30, 2010, at 1:15 PM, Dan Brickley wrote:
On Wed, Jun 30, 2010 at 6:34 PM, Pat Hayes <pha...@ihmc.us> wrote:
On Jun 30, 2010, at 6:45 AM, Toby Inkster wrote:
On Wed, 30 Jun 2010 10:54:20 +0100
Dan Brickley <dan...@danbri.org> wrote:
That said, i'm sure sameAs and differentIndividual (or however
it is
called) claims could probably make a mess, if added or removed...
You can create some pretty awesome messes even without OWL:
# An rdf:List that loops around...
<#mylist> a rdf:List ;
rdf:first <#Alice> ;
rdf:next <#mylist> .
# A looping, branching mess...
<#anotherlist> a rdf:List ;
rdf:first <#anotherlist> ;
rdf:next <#anotherlist> .
They might be messy, but they are *possible* structures using
pointers,
which is what the RDF vocabulary describes. Its just about
impossible to
guarantee that messes can't happen when all you are doing is
describing
structures in an open-world setting. But I think the cure is to
stop
thinking that possible-messes are a problem to be solved. So,
there is
dung
in the road. Walk round it.
Yes.
So this is a point that probably needs careful presentation to new
users of this technology. Educating people that they shouldn't
believe
any random RDF they find in the Web, ... now that is pretty easy.
Still needs doing, but it shadows real world intuitions pretty well.
If in real life you think the Daily Mail is full of nonsense, then
it
isn't a huge leap to treat RDFized representations of their claims
with similar skepticism (eg. see
http://data.totl.net/cancer_causes.rdf for a great list of Things
The
Daily Mail Say Might Cause Cancer).
*However* it is going to be tough to persuade developers to treat a
basic data structure like List in the same way.
Sure. But what they need to grok is that RDF does not have ANY data
structures in it (except maybe triples). It describes data
structures, just
like it describes everything else. It does not PROVIDE data
structures.
Maybe it should - make the case! - but then it will need to change
rather
drastically in its very foundation. Triples describing lists are
not the
same as triples-plus-lists.
The issue is here that RDF started as a metadata format to "describe"
data I believe, and at this point with the Linked Data is now being
transformed into a generic language *for* data, period.
Is this really the case? I wasn't part of the very first RDF
initiative, but ever since I've been involved with it, its purpose was
pretty explicitly supposed to be for representing information - call
it data if you like - rather than anything "meta". I've never read
anything that suggest that RDF is supposed to be describing data. It
is supposed to be describing the world.
The lack of
lists (and hashes, and other things programmers are used to dealing
with) in a reasonable (read "non-XML") syntax is one of the primary
reasons the developer community has moved towards JSON.
Well, Im all for JSON, but JSON is a programming language, not a
language for stating facts in. If anything, JSON would be the
metalanguage here, being used to do things to RDF syntax, I presume.
Now, the question is "Would it be possible to provide a JSON-like
number of data-structures in RDF, and what would this do to its
semantics?" Pat?
Well, it would be up to whoever was designing this RDF/JSON to say
what the logical semantics of these data structures was. The problem
is that as soon as you say what it is, these structures have had their
meaning specified so they aren't 'free' to be used by programmers to,
well, program with. Or, on the other hand, if you let the programmers
have free rein, then they can build things that violate the semantics,
eg suppose we let them write code that tweaks RDF triples into quads,
say: now what do the quads mean?
Given that programming langauge semantics define these things all the
time and it's pretty standard, I imagine its possible.
PL semantics just specifies what the programs do. Its a different kind
of semantic theory. Putting it all together requires one to decide how
the programming processes relate to the assertions of facts.
But it might
make life hard for the principles that RDF was founded upon, i.e. the
sort of "open world" flavor of it all.
Maybe. I think its more a problem of keeping everything kind of
rational. I mean, folk are bothered by a few knotted lists, but
allowing processes to tweak the logical syntax in arbitrary ways is a
far worse nightmare.
Pat
Thus, I imagine it's a trade-off, like most good things in life :)
Pat
Lists are the kinds of
thing we expect to be communicated perfectly or to get some low-
level
error. A lot of developers will write RDF-consuming code that won't
anticipate errors. Hopefully supporting software libraries can take
some of the strain here...
cheers,
Dan
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40 South Alcaniz St. (850)202 4416 office
Pensacola (850)202 4440 fax
FL 32502 (850)291 0667 mobile
phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
