W3C home > Mailing lists > Public > semantic-web@w3.org > September 2007

Re: What if an URI also is a URL

From: Oskar Welzl <lists@welzl.info>
Date: Thu, 13 Sep 2007 23:36:31 +0200
To: semantic-web@w3.org
Cc: Edward Bryant <edward.bryant@gmail.com>, Richard Cyganiak <richard@cyganiak.de>
Message-Id: <1189719391.10882.43.camel@jupiter.hormayrgasse>

Richard,

> Assuming we are talking about a usual web site, http:// 
> www.example.com/ is one specific page: the homepage. Why should it be  
> different? After all, if you open the URI in a browser, you get back  
> a representation of a specific page.

> To learn what a URI refers to, don't look under the hood of the  
> server. Look at the representations returned via HTTP.
> 

I couldn't agree more (at the moment; this whole URI-stuff sends me on
the strangest trips and I change my mind quite frequently - which drives
me nuts...)

The only thing that annoys me is that this approach makes it so
complicated to make statements about a SITE, let alone a web service
that includes more than documents to be retrieved. 

What's a site, anyway? There's no such concept on the web. In fact, a
so-called 'site' is only a collection of documents that needn't even
share the same domain. (My company's website uses 3 main domains and a
dozen I'm probably not aware of. Documents link back and forth across
these domains; to the average user, it's "one site" as all these
documents share the same layout and follow a logical hierarchy.)

Right now I make up arbitrary URIs for sites, using sioc:/rss:link to
point to the main page. While this works well in my own little universe,
its just a mess when comined with, say, foaf-data that expects
foaf:weblog to be a foaf:document, not a madeup:Site that sioc:links to
a foaf:document.

Best thing would be a well-established vocabulary that defines terms
like web site (for collections of documents that somehow belong together
logically), web service (for services that are web sites, but have some
interactive functionality on top), main page for both web service and
web site and a "belongsTo" to express that
our.seconddomain.tld/products/ad45ffh.htm belongs to a web site that has
a main page of our.firstdomain.tld/

Oskar


> Best,
> Richard
> 
> 
> >
> > I just started learning this myself, so someone please correct me  
> > if I am off base here.
> >
> > Ed
> >
> >
> >
> > On 8/30/07, Oskar Welzl <lists@welzl.info> wrote:
> > Am Donnerstag, den 30.08.2007, 22:28 +0200 schrieb Reto Bachmann-Gmür:
> > > But talking about standards, why is this discussion on a list  
> > which has
> > > been replaced by semantic-web@w3.org?
> >
> > dumb boy hit [reply] again; changed it now.
> > Maybe we'll have to change to topic, too, soon: This is going to be  
> > somewhat
> > like "What's the content of an information resource"?
> >
> > Am Donnerstag, den 30.08.2007, 22:30 +0200 schrieb Reto Bachmann-Gmür:
> > > Oskar Welzl wrote:
> > > > Pity, though, that there hardly seems to be an agreement on how to
> > > > handle this issue, so simply by choosing the above URI myself I  
> > will not
> > > > prevent *others* making statements like
> > > > <#thismail> mail:sender < http://oskar.twoday.net>
> > > > when they refer to an update-notification they received from  
> > the weblog.
> > > >
> > > Reading this I think I misunderstood what you mean with "blog" I was
> > > referring to a blog as a changing collection of articles not as
> > > something that sends email. If we agree that an information resource
> > > can't be the mail:sender of a mail then the statement
> > >
> > > <#thismail> mail:sender <http://oskar.twoday.net>
> > >
> > > is necessarily wrong, as a GET request to http://oskar.twoday.net is
> > > responded with a 2XX response and with this response the resource in
> > > unambiguously an information[1]. resource.
> >
> > Well, the "sending mail"-example was certainly the outer limit of
> > nonsense I could possibly construct to get the message through, but I
> > meanwhile think my confusion has a different cause (and it was you who
> > pointed me to it):
> >
> > Lets forget for a minute that a blog is more than just a collection of
> > posts and usually has properties like "allowsCommentsFrom",
> > "offersFeedType", "Blogroll" etc.
> > Assume that it *is* a mere collection of posts, sorted by date, latest
> > first, 10 per page. Period. You type http://my.blog.tld in your  
> > browser
> > to go there, subsequent pages can be reached with
> > http://my.blog.tld/?start=11 etc.
> >
> > In one of your previous posts you wrote:
> > "A Blog is an Information Resource which could be described as
> > an ordered collection of posts, the HTML returned by the webserver is
> > (or should be) a suitable representation of that thing."
> > I didn't like this idea first (and said so, IIRC ;) ...), but it seems
> > logical to me now. *If* we think of a collection of posts and nothing
> > else, it would probably fit the concept of an "Information resource".
> > And what URI other than http://my.blog.tld would we have to name it?
> >
> > On the other hand, the very content of the 10-posts-list returned  
> > by the
> > server (as what could be seen as the HTML-representation of the
> > information resource "blog") is an information resource in its own
> > right. Its "The 10 latest posts from my blog". No other way to  
> > refer to
> > it than via http://my.blog.tld again. Even in this simple construct, I
> > can make statements about http://my.blog.tld  in one RDF-document that
> > contradict each other, like (in OTN, oskars triple notation):
> >
> > http://my.blog.tld  dc:coverage a period from 2003-2007
> > (this was about the blog)
> >
> > http://my.blog.tld  dc:coverage a period from Juli-August 2007
> > (this is about the 1st page of the blog)
> >
> > Same for statements about who commented there etc. - many can be true
> > for only one of the two information resources that are addressed by
> > http://my.blog.tld
> >
> > To get around this, my original assumption was that before using a URI
> > to name something, I should check if its suitable by narrowing the
> > "information resource" as much as possible: take the representation  
> > you
> > get, take all possible interpretations of what it represents (a blog,
> > the first 10 postings, the author himself) and always take the
> > narrowest. What you end up with is, almost always, only a little more
> > than "the document". I like this approach for its simplicity, but it
> > breaks a lot. Take SIOC as an example. sioc:forum/sioc:site is exactly
> > what we're talking about here; they always refer to it via a URI that
> > is, in fact, "the first page of the collection". This is not wrong as
> > such, it just creates ambiguity, which UIRs should not have.
> >
> > (In fact it was my current work on a SIOC-export that confronted my  
> > with
> > this boring question again after so many years.)
> >
> > Now I go the steep way and say that http://my.blog.tld, the blog,  
> > should
> > not be confused with http://my.blog.tld, the most recent posts. The  
> > blog
> > should have its own URI, as "10 most recent posts" is the narrower
> > construct. Next question:
> > I plan to use http://my.blog.tld/ID/names#thisblog as sioc:site and  
> > have
> > an RDF/XML-document at ../ID/names to further define #thisblog. Now  
> > how
> > do I point to the preferred link/bookmark/"entry point" (which is, of
> > course, http://my.blog.tld/) with a well-known vocabulary? I was  
> > tempted
> > to use rss:link, but am very unsure about it... (Not finding a usable
> > hint on Google made me even more uneasy with the whole topic, as this
> > suggests nobody on this planet ever thought of *not* using the URI of
> > the main page as the URI for the whole site.)
> >
> > So you see, even though there might have been a misunderstanding about
> > the concept of a "blog", this wasn't the cause of my problems. Even  
> > when
> > following your 'collection of posts'='information resource'  
> > definition,
> > I get deeper and deeper into trouble.
> >
> > You already got me on a better track once by pointing out the somewhat
> > vague definition of information resource - maybe you got some new  
> > input
> > for me to chew on ;)
> >
> > Thanks,
> >
> > Oskar
> >
> >
> >
> 
> 
> 
Received on Thursday, 13 September 2007 21:36:42 UTC

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