W3C home > Mailing lists > Public > semantic-web@w3.org > August 2015

Re: Naming Conventions for URIs

From: David Booth <david@dbooth.org>
Date: Fri, 21 Aug 2015 11:30:55 -0400
Message-ID: <55D7442F.3000700@dbooth.org>
To: Paul Houle <ontology2@gmail.com>, "semantic-web@w3.org" <semantic-web@w3.org>, "Discussion list for the Wikidata project." <wikidata-l@lists.wikimedia.org>
On 08/20/2015 11:36 AM, Paul Houle wrote:
[ . . . ]
> The production for a QName  cannot begin with a number so it is not
> correct to write something like
>
> dbpedia:100
>
> or expect to have the full URI squashed to that.  This kind of gotcha
> will drive newbies nuts,  and the realization of RDF as a universal
> solvent requires squashing many of them.

I agree.  And although (as Andy pointed out) this particular issue has 
been fixed in SPARQL 1.1 and Turtle 1.1, last I checked not all tools 
had been upgraded to those specs, so it still remains a problem in 
practice.  Personally, as a workaround when converting a natural key to 
a URI, I always prefix the key with an alpha string that suggests what 
it is.  For example instead of the above I might write:

   dbpedia:dbp_100

Another place that URI creation and management causes unnecessary 
headache is when you want to mint a new URI that is relative to an 
existing URI that you don't control.  For example, suppose someone else 
gives me a URI for Alice:

   <http://example/other/alice> a foaf:Person .

My software wants to add some triples about Alice's address, such as:

   <http://example/other/alice> v:address _:b
   _:b v:street "Park St" .
   _:b v:city "Shadyville" .

For SPARQL and other reasons it would be better to use a URI like 
<http://example/other/alice/address> instead of a blank node _:b for 
Alice's address, such as:

   <http://example/other/alice>
         v:address <http://example/other/alice/address> .
   <http://example/other/alice/address> v:street "Park St" .
   <http://example/other/alice/address> v:city "Shadyville" .

But since I do not control Alice's URI, I cannot safely mint a URI that 
is relative to Alice's URI without the consent of the original URI's 
owner.  (Otherwise I would be URI squatting, which is bad practice and 
risky.)

Intuitively I would like the new URI to be somehow derived from Alice's 
URI.  I could mint a URI from my own URI space <http://example/mine/>, 
by concatenating Alice's URI (after escaping) onto mine, such as:

   <http://example/mine/address#http://example/other/alice>

but now I don't have an easy PREFIXed way to write that URI in Turtle or 
SPARQL.  :(  Furthermore, I have to be careful to properly escape the 
original URI before concatenating it, because it might contain 
characters that are not allowed in a fragment identifier.

In my experience URI allocation and management is one of the most 
annoying practical aspects of working with RDF, as compared with JSON, 
for example, where one can just put blinders on and ignore the need for 
global identification.  It would be great if some PhD student or other 
creative person could figure out a good solution to reduce this pain and 
make RDF easier for a wider audience to use.  (New conventions?  A new 
RDF serialization?  Extend RDF?)  JSON-LD is a good step, but still 
doesn't solve the problem.

David Booth
Received on Friday, 21 August 2015 15:31:24 UTC

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