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

Re: homonym URIs (Re: What if an URI also is a URL)

From: Rikkert Koppes <rikkert@finalist.com>
Date: Tue, 12 Jun 2007 06:59:03 +0200
Message-ID: <466E2817.306@finalist.com>
To: Sandro Hawke <sandro@w3.org>
CC: Pat Hayes <phayes@ihmc.us>, semantic-web@w3.org

Sure, forbidding homonyms seems like a gooed idea, but I wonder if this 
is also possible. Doesn't homonym URI alread exist?

To illistrate an example: www.example.com might be (identified as) a 
person's home page. But it might include a link element linking to an 
openId endpoint (www.example.com/openId, say). We do have two different 
URI's for two different things, but www.example.com is also a alias for 
the openId endpoint (by virtue of the link element).

What should we do when making statements about someone owning the site 
and also using the openId alias? Can we safely say that the thing the 
uri identifies (the web site, document) is in fact the openId alias? I 
don't think so. It is the uri itself, so we therefore might contain it 
as a string literal in a statement about the person's openId alias.

Rikkert Koppes (mophor)

Sandro Hawke schreef:
> Pat Hayes <phayes@ihmc.us> writes:
>   
>> Tim, as this discussion gets to the heart of what
>> Ive been trying to argue for several years,
>> please take the comments below as intended in a
>> spirit of analysis rather than just pins and
>> angels.
>>     
>
> Pat, I'm going to jump in here, if you don't mind.  I think my position
> on these issues is pretty much the same as Tim's but I could be wrong.
> I don't argue that John's "dance" isn't required, just that part of the
> Semantic Web version of the dance is: don't make your URIs unnecessarily
> ambiguous.  One might even say: don't pun.
>
>   
>> And what about a URI
>> that I own and wish it to denote, say, the planet
>> Venus, or my pet cat? What do I do, to attach the
>> URI to my intended referent for it?
>>     
>
> You publish a document (an ontology) so it's available through that URI.
> If it's a hash URI, you publish the ontology at the non-hash version.
> If it's a slash URI, you publish the ontology at the far end of a 303
> redirect.  And you content-negotiate HTML and RDF.
>
> So when users paste that URI into their browser, they get the official
> documentation about it.
>
> And when RDF software dereferences that URI, it gets some logical
> formulas which should be understood (like the HTML) to be asserted by the
> URI's owner/host/publisher.  Those formulas constrain the possible
> meanings of that URI, relative to other URIs.  They can't nail a URI to
> Venus, but they can use other ontologies to provide useful (and possibly
> very constraining) information, like that it's an astronomical body with
> a mass of about 5e+24kg.
>
> My advice here is, I confess, not widely followed.  But I hear more and
> more people converging on the idea that this is both practical and
> likely to be sufficiently effective.
>
>   
>> The point surely is that URIs used to refer (not
>> as in HTTP, but as in OWL) do *not* have a
>> standardized meaning. Standards are certainly a
>> chore to create, but they only go so far. OWL
>> defines the meanings of the OWL namespace, but it
>> does not define the meanings of the FOAF
>> vocabulary,
>>     
>
> No, that's up to the owner(s) of the FOAF terms.
>
>   
>> or the URIrefs used in, say,
>> ontologies published by the NIH or by JPL.
>>     
>
> And that's up to the NIH and JPL, respectively.
>
>   
>> The
>> only way those meanings can be specified is by
>> writing ontologies: and finite ontologies do not
>> - cannot possibly - nail down referents
>> *uniquely*. 
>>     
>
> Ah -- there we go.  There must be a long history of this subject in
> philosophy.  Can things ever be nailed down uniquely?  I haven't a clue.
> But that's the wrong question.  In this thread, I don't think we're
> talking about whether we can really be sure what we mean when we say
> such a URI denotes Venus.  Instead, we're talking about whether it's a
> good practice to use a single URI to denote clearly distinct things,
> such as:
>    (1) the second rock from the sun
>    (2) the Roman goddess of love
>    (3) a star tennis player
>    (4) ... etc
> The term "ambiguity" covers both these issues, but we don't need to
> combine them.   The first is a kind of imprecision, a fuzziness, while
> the second is the re-use of a word for a second meaning, a homonym.
> (Homonyms seem to be called "overloading" in computer programming.)
>
> I think we know how to work with homonyms, but since we're engineering a
> new system, it seems like a good design decision to forbid them, doesn't
> it?
>
>     -- Sandro
>
>   
Received on Tuesday, 12 June 2007 04:56:57 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 1 March 2016 07:41:57 UTC