On Jun 21, 2008, at 11:52 PM, Peter Ansell wrote:
Not if you type it with xsd:anyURI...
The you are saying the page is an xsd:anyURI, not a web page.
You aren't saying that all RDF Resource (non-literals) are web pages
though. So why is saying that it is an RDF Resource supposed to
indicate that it is a web page?
It doesn't. But it doesn't say it can't be, which is what you are
doing if you talk about the literal - literals and individuals are
disjoint.
By using foaf:page you add a little more - since the range is
foaf:document, you know that the resource is a document now. It would
be better to have a more refined ontology of things that one lands up
interacting with in a browser window. I'm involved in a couple of
efforts in that direction, as I am sure others are. In foaf, there is
foaf:homepage, but it isn't quite right. Two things to note about it:
(1) Even though it's range is specified as foaf:document, it's
english documentation, which expresses the intention better, says
that the target is "public Web document". It's just that foaf doesn't
have the vocabulary to use as more precise range for this property.
(2) The reason it isn't suitable in this case is that the
documentation says: "The homepage is usually controlled, edited or
published by the thing whose homepage it is". Since in this case the
subject of the page isn't the sort of thing that controls, edits, or
publishes, it doesn't really match, although the hedging "usually"
might allow for it. Best to ask the author (Hi Dan, we know you're
out there ;-) of the ontology and have them clear up the documentation.
Is there no separation allowed between the web and the semantic web
really?
Need there be?
Clearly, there is a big wide world out there with a web that exists
perfectly fine with the semantic constrains ;) IRL!
Sorry, don't know what "IRL" means. But if I get your drift, you are
saying is that the web does not require the Semantic Web to talk
about it. However that doesn't imply that it doesn't or shouldn't.
I thought the semantic web was based on logic not web structures?
Where did you get that idea?
By definition not all URI's are web structures, therefore the basis is
in a non-web scenario, of which web structures occupy a distinct
logical subset. RDF and OWL assume that there are abstract classes,
which are not web structures by any means.
I don't know what an abstract class is.
However, if you are saying that RDF and OWL talk about more than web
structures, you are absolutely right. That means the domain of the
Semantic Web is a set that *subsumes* web pages, not a set
*disjoint* from them.
The semantic web doesn't gain anything from the result of that
page, which
clearly has an
alternative semantic representation available that you are already
looking at when you see the foaf:page (or whatever predicate allows
literals) statement.
It isn't about the result of what you fetch so much as it is speaking
clearly, as I said earlier. The domain of foaf:page is a document.
Neither a
string nor an xsd:anyURI is a document. End of story.
It is clear to me what the string means. And saying it is a
foaf:Document doesn't help with that at all. foaf:Page having a domain
of rdf:Resource doesn't have any more practical benefit than if it
didn't say what its domain was.
To you perhaps. To others it does. For one thing it can be used to do
some basic checking for nonsense statements. (such as the one you
were about to make ;-)
If you accept that the ontology you are using puts xsd:anyURI typed
literals into a given field it is perfectly meaningful to use the
string as you do any other URI string,
If you use another ontology than foaf, with a different relation
whose
domain is an xsd:anyURI, and that relation is documented in such a
way as to
make sense, then sure. I don't happen to see what is gained by
doing that.
The ability to have a string as you say which won't be presumed to be
a semantic resource identifier on its own which people can look at and
resolve themselves.
And?
-
What is a "semantic resource identifier"?
-
I'm still failing to see harm in <http://....>. One can examine an
RDF representation, read that, and resolve that manually as well.
just in a context which won't be interfered with, or interfere
itself
with, the logic based semantic
web rules.
I don't know what you mean by "interfered with" or what connection
you are
making between this particular choice and logic based semantic
web rules. It seems to me that the main benefit of using foaf:page
here is
that a lot of people know what it is supposed to mean.
Do they really gain the benefit specifically from its use as an
rdf:Resource though?
The instances of rdf:Resource are defined to be *everything*. I'm not
sure what you mean by "benefit specifically from its use as an
rdf:Resource", but I don't need to because by definition everything
is a rdf:Resource.
It's like saying: Do I gain specifically from being composed of
matter? That I am is a matter of fact. The question might be of
metaphysical interest, but not practical interest.
Or do they really do a non-semantic retrieval of
the resource? Should they only expect to be able to retrieve machine
readable representations if they resolve this resource?
Who are they?
What is a machine readable representation?
How do you actually say that a specific rdf resource doesn't
actually direct to
an rdf representation as an idenfifier itself.
I'm having trouble parsing this sentence. Could you rephrase it?
The web page is
<http://www.bbc.co.uk/programmes/b00b07kw.html> (the thing that
the URI
denotes)
It isn't an RDF Resource any more than my street and suburb address
though, it is a simple human based locator which doesn't really
have a
need or want to be an RDF Resource IMO.
In both the case of the house, and the case of the web page, there
is the
resource - the house and the web page - and there is the address
of the
house and of the web page (also resources, but different ones). In
discussion, one says different things about the address and the
thing. For
instance,
"http://www.bbc.co.uk/programmes/b00b07kw.html"; has 45 characters.
or <http://www.bbc.co.uk/programmes/b00b07kw.html> uses the
stylesheet
<http://www.bbc.co.uk/programmes/r/23870/stylesheets/decor.css>
or "http://www.bbc.co.uk/programmes/b00b07kw.html"; is a name for
<http://www.bbc.co.uk/programmes/b00b07kw.html>
I don't see why your convention of not dealing with URI's as strings
themselves really helps.
You keep thinking that I am arguing that some convention is useful.
The only thing I am arguing is useful speaking clearly. There is a
difference between the string and the thing it names (when the string
actually names something). If you use the string for both cases one
can't tell, in general, which it is that is your subject of
discourse. Nor can you infer that it even is to be used as a name.
Ambiguous statements work (to a certain extent) with people. They
work to a lesser extent with machines, at least for the moment.
Interestingly the difference between the RDF
resource identifier and the URL in the last one is what I am trying to
get at, just in the opposite way as the last statement is in the wrong
order for RDF.
s/is a name for/is named/ and swap subject and object.
"32 vassar avenue, cambridge, ma, usa" has 36 characters or
<the MIT Stata Center> foaf:depiction
<http://en.wikipedia.org/wiki/Image:Wfm_stata_center.jpg>
or "32 vassar avenue, cambridge, ma, usa" entered into google
maps, will
locate <the MIT Stata Center>
And I am trying to say your last statement exactly. When entered into
a web browser the .html version will produce something they can look
at... Why is it different for addresses?
It's not. There are great many things one can say. foaf:page doesn't
say this. Invent a relation that means what you want it to, document
it well, and use it. David Booth calls this relation hasURI (http://
esw.w3.org/topic/AwwswDboothsRules)
It is a coincidence IMO that it is defined in the same way that RDF
Resources are, and it isn't
useful to mix everything up by presuming that URL's of web pages are
useful as RDF Resources any more than arbitrary string literals.
First, in the RDF world, everything is an rdf:resource, including
rdf:Literals. So they are "mixed up" already. While there were
perhaps
mistakes made in RDF, that web pages are considered resources is most
certainly not one of them. Finally, I'll point out once again that
the issue
here isn't what is or is not a "good" resource. The issue is speaking
clearly. If you want to talk about the literal, by all means do
so, and if
you want to talk about the web page, likewise. But don't confused
one with
the other.
I have never quite understood the reason for putting Literals inside
of "Resources" when you can't say anything about Literals as a subject
except in reverse as the object of a statement and by common-sense you
should be able to state properties of Resources directly rather than
indirectly as RDF provides for the Literal subset.
Me either. Perhaps because they just didn't think that people would
want to say that many things about literals. Don't know. I've heard
it mumbled that if RDF goes through another edit, this might get
fixed. Mostly it's not a problem, unless you want to say something
where both the subject and object are literals, since in the other
case you can invert the relation. In the literal p literal case I've
seen people use the idiom:
_:foo hasLength "45"^^xsd:Integer
_:foo owl:sameAs "http://www.bbc.co.uk/programmes/b00b07kw.html";
(not that i'd particularly recommend it)
or
_:foo hasLength "45"^^xsd:Integer
_:foo rdf:value "http://www.bbc.co.uk/programmes/b00b07kw.html";
(less of evils)
I personally think its a bad idea to smudge the differences by saying
all web pages are semantic resources
All web pages are rdf:Resources. What is this "semantic resource" you
speak of?
, as they aren't... Many have no
inherent RDF semantics whatsoever and hence can't be reasonably used
as the subject of statements.
Umm...
<http://www.bbc.co.uk/programmes/b00b07kw.html> is about an episode
of the television programme Dr. Who.
"http://www.bbc.co.uk/programmes/b00b07kw.html"; is a string of length
45.
It would be much better if by default they were thought of as
Literals and kept as objects of statements in
semantic terms.
Well, I can see that you are making this assertion, but I can't
understand the reasoning behind it.
Regards,
Alan
