RE: URIs

Hi, Alan,

This is an important topic and I think it should be an action item in one of
our task groups.

This is my two cents about the topic.

> 1) The relationship between the use of a URI in a 
> representation and what it dereferences to, if anything. The 
> possibilities seem to be:
> 
>    a) The identifier is not intended to be dereferencable. In that   
> case the info: scheme was suggested for the form of the uri, 
> as that is explicitly not dereferenceable.
> 
>    b) The URI is used primarily as a name. Insofar as we want 
> use names, it is important there be some stable URIs. Of 
> course it doesn't hurt if the URI becomes dereferenceable at 
> some point, and it would even be nice, so let's leave open 
> that possibility (but caveats in discussion below)
> 
>    c) Any URL we use needs to be able to be dereferenced to something.
> 
>    d) Any URL we use needs to be able to be dereferenced to 
> the thing it is (and not dereferenced if you can't do that). 
> It's only meaning is what it dereferences to.

The use of a URI is all of the above.  If you see it from a programming
point of view, URI isn't that kind of special to any variable identifier of
any (dynamic) programming language.  The only difference is that storage.
For URI, it is the web, for regular language, it is the physical memory of a
computer.

For example, given a javascripts variable,

var gene;

Would you guess the nature of this variable from its name? Of course you
don't.  You must do some  checking before you use it.

It is the same for a URI,

URI http://www.example.com/gene;

You need to dereference the "gene" variable in order to understand it and do
something meaningful about it.  

Answer to (1a), Of course, you can have "variables" that are not intended to
be dereferenced, in Java script, the type "undefined" is similar to a "404".
(Please note, a 404 does not mean that the URI does not exist, it just
implies that at current time, it cannot be dereferenced.) It is not wrong to
define an "undefined" variable, it is just not much use of it.
(1b) URI is just the name that refers a location on the WEB, so it of course
is a name.
(1c,d) The issue is not "needed" to be or not, it is all about what you want
to use it.

> 2) What a URI refers to. Some of this conversation was made 
> in the form of a discussion about what reasonable arguments 
> to owl:sameAs are - for example should one say that 
> http://www.expasy.org/uniprot/
> P04637 is the sameAs http://eutils.ncbi.nlm.nih.gov/entrez/eutils/
> efetch.fcgi?db=protein&id=NP_000537.
> 
> Another part of the conversation talked in terms of whether the URI
> http://www.expasy.org/uniprot/P04637 should, for our 
> purposes, refer to a database record or to a thing in the 
> world - Human P53 proteins.

I think this is an application issue rather than an architectual issue.
Hence, it will be a design issue. For the first example, in its current
state, it is "fine" because what is returned back is an text document.
Then, whoever made such an assertion considers the two electronic documents
are semantically equivalent.  However, if you intended to make either URI to
represent the entity of "Cellular tumor antigen p53", it is wrong.  The
latter is a non-information resource.  The entity can not be dereferenced.
What can be dereferenced is the "description" about "Cellular tumor antigen
p53".  In this case, the dereference should first return a 303 followed by
the link to an electronic document, which would ideally be an RDF but any
other text doucments are fine too.  

> 3) Something I will call the social aspect of URIs, for lack 
> of a better term. By this I mean those aspects process we go 
> through to come to a shared use of of URI. Under this 
> category there is the ontology building, the strategies for 
> connecting pieces of information generated by different 
> groups. There was a bit in the conversations where people 
> were arguing about whether using sameAs for mapping was 
> pollution or a necessity, for instance. An important part of 
> this in our context is how to define the use of URLs to 
> things where there was not rigorous ontological engineering 
> applied to create careful definitions, things like 
> terminologies and entries in gene databases.

How to use of URI should be defined by W3C not by individual user group.
Otherwise, you will break one web into a bunch of smaller island.  That will
not be what you wanted it for.

Xiaoshu

Received on Monday, 19 June 2006 13:50:49 UTC