W3C home > Mailing lists > Public > www-tag@w3.org > July 2007

Re: Terminology Question concerning Web Architecture and Linked Data

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 30 Jul 2007 14:49:46 -0500
Message-Id: <p06230911c2d3f147554e@[]>
To: Hugh Glaser <hg@ecs.soton.ac.uk>
Cc: Tim Berners-Lee <timbl@w3.org>, Chris Bizer <chris@bizer.de>, <www-tag@w3.org>, <semantic-web@w3.org>, Linking Open Data <linking-open-data@simile.mit.edu>

>I am trying hard to keep up (I suspect like many), and was hoping someone
>would address a concern I have; forgive me if I missed it somewhere in the
>I have hung this off this message from Tim, which seems the most relevant.
>And congratulations on the Linked Data Tutorial - a really useful document.
>So here we go:
>On 25/7/07 14:35, "Tim Berners-Lee" <timbl@w3.org> wrote:
>>  (Going back to the original question, as it is much simpler than much
>>  which follows!)
>>  On 2007-07 -07, at 08:43, Chris Bizer wrote:
>>>  Question 3: Depending on the answer to question 1, is it correct to
>>>  use owl:sameAs [6] to state that http://www.w3.org/People/Berners-
>>>  Lee/card#i and http://dbpedia.org/resource/Tim_Berners-Lee refer to
>>>  the same thing as it is done in Tim's profile.
>>  Yes.
>So Tim absolutely right.
>This is an entirely logical thing to say.
>These two NIRs (Non-Information Resources) should be considered the same.

(Aside) I wish folk would not say 'two' when there is only one. Two 
NIRs should never be considered the same: rather, two names may refer 
to the same, single, NIR.

>But it is important to consider how this statement will be used, and worry
>whether there may be unexpected consequences.
>As we now know, the URIs should be resolvable, and so interesting Semantic
>Web applications will use the URI to get the Description (or whatever we
>call it), probably going via a 303.
>So my SW app will get the RDF of them both, and add it to my triplestore,
>along with all the other linked data.
>Tim, as often, is a good example.
>Consider the places Tim works (W3C, MIT, Southampton, I guess).
>It is likely that each will publish RDF about him, hopefully using an agreed
>ontology (one day!).
>Now comes the rub.
>If you put all this in one triplestore, with the owl:sameAs assertions, then
>it will not be possible to distinguish where facts came from, or rather
>which facts are associated with which others.

Whoa, careful. It will probably will be >>possible<< to distinguish 
this, in fact. It might be that unwanted consequences are entailed by 
the combination of the various RDF graphs and the sameAs, but a 
careful querying process should be able to determine which of the 
various triples are present and even whether they are linked. One 
simple way is to query under sub-OWL entailment, for example, which 
can be little more than a direct syntactic matching process (see 

>Perhaps 3 job titles, 3 telephone numbers and 3 institution addresses will
>be returned from the appropriate SPARQL queries, and there will be no
>(legal) way of working out which corresponds to which.

That would be a symptom of poor RDF/OWL usage, though. Assertions in 
RDF are not supposed to be local-context-sensitive in the way you 
seem to be assuming. So for example it would be a mistake to simply 
assert, in the w3c page, that Tim's status WAS Director. It ought to 
say that a relationship holds between him and the entity he is the 
Director of, i.e. the W3C; so that this stays true even when it is 
moved somewhere else on the Web. In fact, I suggest that as a basic, 
fundamental principle of any 'web logic' is that assertions in it 
should have the same meaning wherever they occur on the Web (see for 

>So I can infer that the person http://www.w3.org/People/Berners-Lee/card#i
>is a Professor at MIT, or a Senior Research Scientist at W3C, or Director at
>Southampton, none of which we consider true.
>(Of course, this was the intention of the sameAs assertion.)
>I suggest that this is a bad state of affairs

It would be, yes, but it should not arise if the RDF is written properly.

>, and applies to any NIR, not
>just people.

It applies to any R, I or NI. Its really nothing to do with the 
nature of the thing named.

Pat Hayes
IHMC		(850)434 8903 or (650)494 3973   home
40 South Alcaniz St.	(850)202 4416   office
Pensacola			(850)202 4440   fax
FL 32502			(850)291 0667    cell
phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
Received on Monday, 30 July 2007 19:50:02 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:32:53 UTC