W3C home > Mailing lists > Public > public-lod@w3.org > June 2008

Re: bbc-programmes.dyndns.org

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Sun, 22 Jun 2008 00:42:39 -0400
Message-Id: <9C15A420-BE33-441D-AA10-8950C84EC9B1@gmail.com>
Cc: "Richard Cyganiak" <richard@cyganiak.de>, "Nicholas Humfrey" <Nicholas.Humfrey@bbc.co.uk>, public-lod@w3.org
To: "Peter Ansell" <ansell.peter@gmail.com>


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
Received on Sunday, 22 June 2008 04:43:22 UTC

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