On Jul 1, 2010, at 9:42 AM, Kingsley Idehen wrote:
Pat Hayes wrote:
On Jun 30, 2010, at 3:49 PM, Kingsley Idehen wrote:
Pat Hayes wrote:
On Jun 30, 2010, at 1:30 PM, Kingsley Idehen wrote:
Nathan wrote:
Pat Hayes 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.
Could we also apply that to the 'subjects as literals' general
discussion that's going on then?
For example I've heard people saying that it encourages bad
'linked data' practise by using examples like { 'London' a
x:Place } - whereas I'd immediately counter with { x:London a
'Place' }.
Surely all of the subjects as literals arguments can be
countered with 'walk round it', and further good practise could
be aided by a few simple notes on best practise for linked data
etc.
IMHO an emphatic NO.
RDF is about constructing structured descriptions where
"Subjects" have Identifiers in the form of Name References
(which may or many resolve to Structured Representations of
Referents carried or borne by Descriptor Docs/Resources). An
"Identifier" != Literal.
What ARE you talking about? You sound like someone reciting
doctrine.
Literals in RDF are just as much 'identifiers' or 'names' as URIs
are. They identify their value, most clearly and emphatically.
They denote in exactly the same way that URIs denote.
"23"^^xsd:number is about as good an identification of the
number twenty-three as you are ever likely to get in any
notational system since ancient Babylonia.
Yes, but ancient Bablyonia != World Wide Web of Structured Linked
Data, slightly different mediums with some shared
characteristics :-)
The World Wide Web is becoming a Distributed DBMS (in my eyes).
Thus, unambiguous naming matters.
A topic for a longer discussion; but irrelevant here, since typed
literals are as unambiguous as a name can possibly get.
Literal Subjects aren't a "show stopper" per se. (esp. for local
RDF data). My gripe simply boils down to the nuisance factor
introduced by data object name ambiguity in a distributed data
object oriented realm such as the emerging Web of Linked Data.
What does ""23"^^xsd:number " mean to anyone in a global data space?
It means the number twenty-three, everywhere and for all time,
because this meaning can be computed from the very syntactic form
of the name. How unambiguous can something get?
Pat,
Re. RDF's triples, What is a Subject? What is an Object?.
"subject' refers to the first element in a triple, "object" to the
last. One might as well call them 'first' and 'third'. The names
'subject' and 'object' are used purely for convenience, and have no
formal or semantic significance.
If they are the same thing, why on earth do we use Names (with
implications) to describe the slots in an RDF triple?
I do not understand the question here well enough to provide an
answer. Have you actually read the RDF spec documents? The RDF syntax
model and the semantics?
I've only once seen the RDF triple referred to as O-R-O (by @danbri)
i.e., Object-Relation-Object.
IF you read the specs, however, it is abundantly clear that this is
what an RDF triple means, viz. that a relation holds between two
objects (I prefer "things", but....).
In addition, I don't see Information and Data as being the same
thing. Information (as I know it) is about Data + Context. Raw Data
(as I know it) is about: a unit of observation and deemed worthy of
description by its observer. You have to give Names to subject of a
description. "23"^^xsd:number isn't a Name.
Why do you say this? It is certainly as much a name as, say, "Patrick
J. Hayes". It is a well-formed string which denotes something, and its
denotation is perfectly clear, in fact computable. So, it is a name. I
challenge you to specify what you mean by "Name" in such a way that it
excludes literals as names, other than by simply reiterating your bare
claim that they are not.
**
I guess my own subtle mistake (re. this thread) is deeming
Identifiers and Names to be equivalent , when they aren't :-) Of
course, one can use an Identifier as a Name, but that doesn't make
them equivalent.
**
One clear point of divergence here is that I am focused on the Web
as Dist. DBMS that leverages 3-tuples + HTTP URIs in the S, P, and
optionally O slot (aka. HTTP based Linked Data).
To conclude:
Name != Identifier.
I believe Subject == Name (an Identifier based Name) re. RDF triples
otherwise the triple should be described as: O-R-O or O-P-O.
I believe an S-P-O triple is a piece of information (Data Object has
a Name and at least one Attribute=Value pair).
What I desscribe actually has zilch to do with RDF as I am inclined
to believe you see RDF :-)
I see it the way the RDF specifications describe it. I am genuinely
not quite clear how you see it, but it seems to have very little to do
with the way it is specified. Perhaps you would be better off using
something other than RDF.
Pat
Thus, in a way, the literal-subject debate may simply help everyone
understand and accept that RDF != Linked Data. Thus, providing
additional proof that RDF isn't mandatory or even required re.
delivery of HTTP based Linked Data.
RDF based Linked Data != RDF. They are different things, clearly.
We can't have it both ways (** Pat: not for you, that's for those
that deem RDF and Linked Data inextricably linked **).
BTW - I still have no idea if RDF and RDF/XML are really distinct.
HTML and N3 built the Web of Linked Data, but N3 remains a 2nd or
3rd class citizen whenever we talk about the pragmatic aspects of
what continues to be inappropriately labeled as an RDF virtue i.e.
Linked Data.
Danbri:
I agree with the essence of your earlier post!
Kingsley
Pat
I know the meaning of: <http://km.aifb.kit.edu/projects/numbers/web/n23#this
>, based on the resource I deref at: <http://km.aifb.kit.edu/projects/numbers/web/n23
>
Kingsley
Pat Hayes
If you are in a situation where you can't or don't want to mint
an HTTP based Name, simply use a URN, it does the job.
Best,
Nathan
--
Regards,
Kingsley Idehen President & CEO OpenLink Software
Web: http://www.openlinksw.com
Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter/Identi.ca: kidehen
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Regards,
Kingsley Idehen President & CEO OpenLink Software
Web: http://www.openlinksw.com
Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter/Identi.ca: kidehen
------------------------------------------------------------
IHMC (850)434 8903 or (650)494
3973
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
--
Regards,
Kingsley Idehen President & CEO OpenLink Software Web:
http://www.openlinksw.com
Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter/Identi.ca: kidehen
------------------------------------------------------------
IHMC (850)434 8903 or (650)494 3973
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