Juan Sequeda [2013-06-12T15:13]:
If I have a NULL for the column age, we can all assume that everybody has an
age (there exist an age), but I don't know what it is. So it would be safe
to have x :age _:age
Do dead persons have an age?
--
Karl Dubost
http://www.la-grange.net/karl/
Do dead persons have an age?
That depends. A body of a dead person belonged to a living person. The idea of
a person can live on. Indeed there are still anniversary celebrations of famous
people's life events. The work of a person can also live on. People are partly
defined by their ideas and
On 14/06/2013 11:35, Andy Turner wrote:
Do dead persons have an age?
That depends. A body of a dead person belonged to a living person. The idea of
a person can live on. Indeed there are still anniversary celebrations of famous
people's life events. The work of a person can also live on.
On 14/06/2013 11:35, Andy Turner wrote:
Do dead persons have an age?
That depends.
Can depend on what you mean by person and what you mean by age. If me
denotes me in an enduring sense, i.e. I am the same person I was
yesterday, then my age is a function of time, I'm older today than I was
Given a document date, age is an important feature in disambiguating identity
since it loosely relates to date of birth. It's also used in many situations
where a date of birth would create personal privacy issues.
Most properties change over time. The LOD community has a bias for facts that
a.g.d.tur...@leeds.ac.uk
To: 'Karl Dubost' k...@la-grange.net; Juan Sequeda juanfeder...@gmail.com
Cc: public-lod public-lod@w3.org
Sent: Friday, June 14, 2013 5:35 AM
Subject: RE: Representing NULL in RDF
Do dead persons have an age?
That depends. A body of a dead person belonged to a living person
Precisely, they should have both: projected age and age at death.
On 14 Jun 2013 11:37, Andy Turner a.g.d.tur...@leeds.ac.uk wrote:
Do dead persons have an age?
That depends. A body of a dead person belonged to a living person. The
idea of a person can live on. Indeed there are still
that this was good food for thought.
Best wishes,
Andy
http://www.geog.leeds.ac.uk/people/a.turner/
From: Juan Sequeda [mailto:juanfeder...@gmail.com]
Sent: 12 June 2013 20:13
To: Tim Berners-Lee
Cc: Steve Harris; Pat Hayes; Sven R. Kunze; public-lod
Subject: Re: Representing NULL in RDF
It depends.
If I
Just for the record, I was suggesting the blank node only to represent the
***case described below***, not as a general replacement for NULL, which seems
to have many meanings. In the original message this was one of four or five
possible NULL meanings.
Pat
On Jun 12, 2013, at 11:08 AM, Tim
On 2013-06 -10, at 19:48, Steve Harris wrote:
On 2013-06-09, at 20:36, Pat Hayes pha...@ihmc.us wrote:
...
- value uknown (it should be there but the source doesn't know it)
Actually that piece of information could be written down in a RDF Schema
graph like this:
It can be written far
It depends.
If I have a NULL for the column age, we can all assume that everybody has
an age (there exist an age), but I don't know what it is. So it would be
safe to have x :age _:age
Juan Sequeda
+1-575-SEQ-UEDA
www.juansequeda.com
On Wed, Jun 12, 2013 at 11:08 AM, Tim Berners-Lee
Right, but you have used out of band information to know that everyone
has an age. No automated process could know that. null in SQL only
indicates the absence of information, and that is most naturally
indicated in RDF by the absence of a triple, just as the RDB-to-RDF
Direct Mapping
David,
You are right and I should have clarified that.
First of all, nulls in rdbms are... hairy.
If you have outside knowledge, which could be given to an automated system,
then generating a triple with a blank node *could* be the right thing to
do. But it all depends on the ... semantics :)
uses). I think the discussion of “Representing NULL in RDF” revealed many of
those little peculiarities and nuances of not knowing everything:
we make no statement about the existence of that property relation for that
instance (we just don’tk know)
we know of the existence for that particular
Yes, from the wording, I do agree with you.
However, as the entailment rule says, your conclusion is correct, but the other
way round might not. That you know, that there is something for that particular
instance, does not imply the necessity for each instance of that rdf:type.
That is, when
On Jun 11, 2013, at 2:03 PM, Sven R.Kunze wrote:
Yes, from the wording, I do agree with you.
However, as the entailment rule says, your conclusion is correct, but the
other way round might not. That you know, that there is something for that
particular instance, does not imply the
Zitat von Pat Hayes pha...@ihmc.us:
On Jun 11, 2013, at 2:03 PM, Sven R.Kunze wrote:
Yes, from the wording, I do agree with you.
However, as the entailment rule says, your conclusion is correct,
but the other way round might not. That you know, that there is
something for that particular
On 2013-06-09, at 20:36, Pat Hayes pha...@ihmc.us wrote:
...
- value uknown (it should be there but the source doesn't know it)
Actually that piece of information could be written down in a RDF Schema
graph like this:
It can be written far more simply in RDF just by using a blank node:
Zitat von Steve Harris steve.har...@garlik.com:
On 2013-06-09, at 20:36, Pat Hayes pha...@ihmc.us wrote:
...
- value uknown (it should be there but the source doesn't know it)
Actually that piece of information could be written down in a RDF
Schema graph like this:
It can be written far
A One could model this piece of information like this:
:s rdfs:inapplicableProperty :p.
Hmm. What would the semantics of this be? Can you write any
entailment rules for it? I imagine this might be one, for example:
x rdfs:InapplicableProperty p .
x p y .
are unsatisfiable (inconsistent),
I heard somebody saying mapping from RDB to RDF? :)
In the RDB2RDF Direct Mapping [1], we do not generate a triple for null
values.
We also studied the direct mapping in the case that there are null values
in our WWW2012 paper [2]
[1] http://www.w3.org/TR/rdb-direct-mapping/
[2]
On Jun 5, 2013, at 8:42 AM, Sven R. Kunze wrote:
Hi Jan,
some ideas I would like to elaborate to you:
I was doing some comparison of relational databases and Linked Data and ran
into the problem of representing an equivalent of database NULL in RDF.
Interesting starting point as
Hi Jan,
some ideas I would like to elaborate to you:
I was doing some comparison of relational databases and Linked Data
and ran into the problem of representing an equivalent of database
NULL in RDF.
Interesting starting point as relational databases actually do not
support your usage
When you are trying to work out how to model something, try consuming the RDF
proposed.
It pretty quickly becomes obvious what are some bad things to do.
Either because you get the wrong answers, or because the queries you want to
do are really hard.
the you can concentrate on the choice from a
On Jun 4, 2013, at 5:31 AM, Jan Michelfeit wrote:
Hi,
NULL most often simply represents that the value is not known, in my
experience
So another conclusion of this discussion can be that unknown is the most
sensible default interpretation if the triple is not there and there is no
To: Jan Michelfeit
Cc: public-lod@w3.org
Subject: Re: Representing NULL in RDF
If there is a *standard or generally accepted* way of doing things, then, as
has been pointed out, it is to ignore it.
Or rather the norm is that NULL (and unknown and anything else like - I'll
use NULL for shorthand
Hi,
NULL most often simply represents that the value is not known, in my
experience
So another conclusion of this discussion can be that unknown is the most
sensible default interpretation if the triple is not there and there is no
indication of the other cases.
I think that you have to
On 2013-06 -03, at 22:39, Jan Michelfeit wrote:
Hi,
thank you all for your answers.
... One represents a null by failing to include the relationship
... RDF semantics make no assumptions about what the absence of a
proposition/statement means
I agree. The question was actually about
Ji Jan,
On 4 Jun 2013, at 11:31, Jan Michelfeit michelfeit@gmail.com
wrote:
Hi,
NULL most often simply represents that the value is not known, in my
experience
So another conclusion of this discussion can be that unknown is the most
sensible default interpretation if the triple is
was not very clear.
Andy
http://www.geog.leeds.ac.uk/people/a.turner/
-Original Message-
From: Hugh Glaser [mailto:h...@ecs.soton.ac.uk]
Sent: 04 June 2013 12:00
To: Andy Turner
Cc: Jan Michelfeit; public-lod@w3.org community
Subject: Re: Representing NULL in RDF
Hi Andy,
On 4 Jun 2013, at 11:24
Hi,
I was doing some comparison of relational databases and Linked Data and ran
into the problem of representing an equivalent of database NULL in RDF.
I was surprised I haven't found any material or discussion on this topic (found
only [1]) - is there some?. I believe it would be beneficial
Hi Jan,
That's because nulls are generally not represented in Linked Data by design.
One represents a null by failing to include the relationship.
Regards,
Dave
On Jun 3, 2013, at 4:38, Jan Michelfeit michelfeit@gmail.com wrote:
Hi,
I was doing some comparison of relational
Hi David, Jan,
This came up in a recent modelling discussion around Open Annotation[1] and
its use in Shared Canvas[2].
Open Annotation has a Choice resource (think rdf:Alt) where, for example,
the body of the annotation could be an HTML document or the equivalent text
in PDF from a different
: Montag, 3. Juni 2013 09:44
To: Jan Michelfeit
Cc: public-lod@w3.org
Subject: Re: Representing NULL in RDF
Hi Jan,
That's because nulls are generally not represented in Linked Data by design.
One represents a null by failing to include the relationship.
Regards,
Dave
On Jun 3, 2013, at 4:38
Jan Michelfeit michelfeit@gmail.com writes:
I was doing some comparison of relational databases and Linked Data and ran
into the problem of representing an equivalent of database NULL in RDF.
I was surprised I haven't found any material or discussion on this topic
(found only [1]) - is
To: Jan Michelfeit
Cc: public-lod@w3.org
Subject: Re: Representing NULL in RDF
Hi Jan,
That's because nulls are generally not represented in Linked Data by design.
One represents a null by failing to include the relationship.
Regards,
Dave
On Jun 3, 2013, at 4:38, Jan Michelfeit
Cheers
Michael
-Original Message-
From: David Wood [mailto:da...@3roundstones.com]
Sent: Montag, 3. Juni 2013 09:44
To: Jan Michelfeit
Cc: public-lod@w3.org
Subject: Re: Representing NULL in RDF
Hi Jan,
That's because nulls are generally not represented in Linked Data by design
On 03/06/13 15:31, Robert Sanderson wrote:
Our solution was to use rdf:nil, but we would be happy to change that
if there is a more appropriate approach.
That was my suggested solution last time this came up on list. It does
make rdf:nil a member of the property's range though, which
Hi,
thank you all for your answers.
... One represents a null by failing to include the relationship
... RDF semantics make no assumptions about what the absence of a
proposition/statement means
I agree. The question was actually about *distinguishing* between the mentioned
cases.
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