Matthias Samwald wrote:
Even if the description of a "resource" in the URI rfc say
that it can refers to actual "things", we only have their RDF
representations.
The fact that we might only be able to retrieve RDF through the web
does not mean that the URI http://example.org/eiffel_tower cannot
designate a physical object. Please elaborate.
No just in relation with the Web. Practically speaking, the Web is only
a way to communicate the RDF description of this resource. I Could send
you a letter where I wrote all the RDF+N3 that you can transcript and
put in your triple store. I don't need the Web to publish RDF... but
hell, the Web is an easy way to communicate this kind of stuff :)
So, what this mean? This mean that in a RDF World only (see it as a
triple store on an un-connected computer (un-connected to any kind of
network)), you are still manipulating RDF representations of Things.
Well, what is a Class and what is an Individual of a Class? The line
is gray, and and someone's class will be another person's individual.
Example: An individual of a tower exists at a certain place at a
certain time (e.g., the Eiffel tower is currently located in Paris).
The class of towers is 'made up' of a multitude of towers at many
times and places. It is very easy to distinguish class from individual
when looking at physical objects. Of course, making such distinctions
gets much harder with more abstract things such as 'concepts' or 'data
objects'. Which, in turn, makes it harder to know where to place
relations such as owl:sameAs, or to create ontologies that enable
automated reasoning and consistency checking. This is why I am a bit
critical about using such abstractions as the foundations of a large,
hopefully somewhat coherent Semantic Web. The identity between
resources named by URIs and shared semantics are the nodes that hold
everything together. If they are too loose, everything starts to drift
apart, and meaningful data integration on a large scale becomes
impossible.
Sure that some example are clearer than others. But there are always
this gray line that can easily be one thing or the other :)
But one thing I say is: we *have to* try to make it as coherent as
possible. But I fear that the semantic web won' ever be coherent. This
is a characteristic that we have to work with, to assess, in order to
create value out of this incoherent World :)
There are certainly best practices such as DOLCE and BFO, but these
are not sacred books, and different usecases will have an hard time
on them.
DOLCE and BFO are foundational ontologies, not practices. The question
is: should using such foundational ontologies become a practice?
But since we are in a Web of Representations, there will be errors
and inconsistencies (there are on the Web, and there will be on the
Semantic Web)...
And this is normal: my representation of the World, is not the same
as your Representation of the World.
Probably true, and this is why 'representations' are not very useful
for data integration. We need to postulate the existance of an
external reality before we can actually talk about errors and
inconsistencies.
Many of us are mixing up questions of epistemology (how we as persons
can gain knowledge) with questions of ontology (how things are in
reality). I emphatically agree with your subjectivist / constructivist
approach towards epistemology -- the way I perceive the world might be
very different from the way you perceive the world. However, the
differences in our cognitive representations while watching the Eiffel
tower do not lead to the existance of two separate Eiffel towers in
reality (ontology).
No, certainly not. But I can "describe" the Eiffel tower with some
characteristics, where you can "describe" the Eiffel tower with other
characteristics: two representations (in RDF using different ontologies?
:) ) of the same "Thing". For example, my URI is a URI of "my"
description of the Eiffel tower, where your URI is the URI reffering to
another representation of the same "thing". However, no URI refers to
the actual "Thing", but only different representations of the same
"Thing" :)
I do believe that we only refers to "representations" in RDF.
The human ability to accept the existance of a consensual external
reality was a key that enabled the development of science and
technology, for testing hypotheses, developing theories and
integrating many small pieces of human experience into a coherent,
testable and shared view of reality. We should not weaken the
practical advantages of this ability by a too radical subjectivism.
But this is just philosophical.... In reality, in my daily working
life.... I refers to objects that have properties. I don't care if one
name it an infroamtion resource, a web document, a Thing, etc. What I
check is: is this URI in one of my triple store? No? Then can I resolve
this URI on the web? yes? Is there RDF? Yes? Is this RDF describing this
URI? yes? then lets do something with it!
I want to do something usefull (even if not perfect) with these things!
Take care,
Fred
