Re: Some Requirements

[Some of the issues raised here are, I believe, tangential to the SW
meaning discussion.]

From: Sandro Hawke <sandro@w3.org>
Subject: Some Requirements
Date: Wed, 24 Sep 2003 08:13:26 -0400

> On behalf of RDF authors everywhere, I'd like to make a URI which is
> usable in several, simultaneous ways: 
> 
>   r1.  As a not-overloaded name, essentially a logical constant term,
>        as specified in RDF Semantics [1].   The URI will be my name
>        for something; others may make other names for the thing or
>        reuse my name for it. 

Seems already covered.

>   r2.  As a web page address for human-readable content, working in
>        currently-deployed browsers, giving users direct access to web
>        content which I supply associated with the URI;
> 
>   r3.  As a web address for RDF/XML content, allowing simple systems
>        to fetch a small to medium size knowledge base, which I supply,
>        associated with the URI

Can't you use content negotiation for this?  

>   r4.  As the address of a query answering service, allowing more
>        complex systems faster access to larger knowledge bases, which
>        I also supply associated with the URI

I don't know how this would work.  Which knowledge base?  How is it related
to the URI reference with optional fragment identifier?

It seems to me that you can already do all this.  Use a URI reference with
a fragment identifier as the name.  The web page and the RDF/XML content
(and maybe OWL content (and maybe FOL content (and ...))) can all live at
the URI address.  The query answering system could also live there, I
guess.

So you have

	http://sandro.org/foaf#sandro		for the name
	http://sandro.org/foaf.html		for the human readable page
	http://sandro.org/foaf.rdf		for the RDF/XML content
	(http://sandro.org/foaf.owl		for the OWL content)
	http://sandor.org/foaf#sandro?...	for other purposes

All, except the last, would be accessible via
http://sandro.org/foaf#sandro.  The last, I think, needs extra parameters,
and thus can't be just http://sandro.org/foaf#sandro.  

This has the advantage that related names can share URIs.

You could even use redirection to use a URI reference without a fragment
identifier.  I think, however, that this is a mistake.

> I can think of a few other uses, but if you can give me these four, i
> think I can figure out the rest.
> 
> Also, ideally:
> 
>    x1.  This would all work beyond the time over which I can
>         reasonably expect to control any particular domain name or
>         website;

This is *much* harder.  I believe that it would need a significant upgrade
to WWW mechanisms, essentially a way of specifying a temporal component in
URIs and redirecting somehow based on this temporal component.  I don't
see this happening, ever.

>    x2.  This would work even if a community of use arises which
>         disagrees with me about what the URI names.  I made it
>         up, I was the first to use it, no one should be able to
> 	make me into a liar by convincing people it meant something
>         different. 

I think that most solutions will have this property.

> For example, one of my little projects is to implement an OWL
> reasoner.  I call it Surnia, and I'd like to tell the world about it
> using all appriate means.  Basically that means I need a website for
> it (r2 above), but I also want to support RDF applications talking
> about it (r1) and learning about it (r3 and r4).
> 
> More specificly, the OWL Test Results page [2] needs an r1-style URI
> for Surnia so it can merge results from different sources, an r2-style
> URI so users can click to get more information, and r3- or r4- style
> URIs so it can show users data about it.  Actually, it doesn't *need*
> any of these and it doesn't really have any of these right now,
> because so far I haven't been able to make a URI like I want!  So
> instead there are three different URIs in use (no r4 yet), which is
> getting pretty clumsy.

Why not just use http://sandro.org/surnia# ?  I don't see why this wouldn't
work?  (Maybe I don't understand content negotiation, but I think that
requestors can get the .html document and the .rdf document depending on
how they ask.)
> 
> About this point, settling for having three or four different URIs
> starts to look okay, but if I do that, I'm certainly not going to use
> an HTTP URI for r1 (it buys me nothing), ... so keep that in mind if
> you urge settling.
> 
> As another example, I have a digital camera with which I've taken
> 3000+ pictures in the past two months (!).  I'd like to give each of
> those pictures an r1 URI so I can record information about the
> pictures.  These are mostly pictures of my kids, so I really need x1:
> I want the pictures and metadata to co-exist happily in 50 years.

I suggest that you bring this up with the gods of the WWW.  Or perhaps you
need to design a new way of sharing information between computers! The
Semantic Web isn't going to have anything to say on this issue, I think.

> Also I want r2 URIs, so people can see the pictures!  And r3 and r4
> URIs so my photo-browser applications can search for pictures and tell
> me about them, along with displaying them.  If all four URIs could be
> the same, it would sure make it easier to keep this huge pile sorted
> out.

I think that you can already do this, modulo browsers and other tools not
adequately supporting you.

>     -- sandro
> 
> [1] http://www.w3.org/TR/2003/WD-rdf-mt-20030905/#urisandlit
> [2] http://www.w3.org/2003/08/owl-systems/test-results-out

Peter F. Patel-Schneider

Received on Wednesday, 24 September 2003 09:37:39 UTC