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Re: Upcoming wave of quad/namedgraph implementations ,was: Reification - whats best practice?

From: Andrew Newman <andrew@tucanatech.com>
Date: Mon, 13 Sep 2004 09:07:31 +1000
Message-ID: <4144D6B3.2040607@tucanatech.com>
To: www-rdf-interest@w3.org

Richard Cyganiak wrote:
> 
> Am 10.09.2004 um 13:32 schrieb Andrew Newman:
> 
>> The main problem we've had with named graphs is that it can be a pain 
>> on a machine that has multiple names or names that change over time.  
>> If I create a models based on machine names called 
>> "http://192.168.10.1/foo" and then move to another network and 
>> suddenly it's "http://10.0.0.42/foo" then all my existing queries stop 
>> working.  I now prefer URNs for models not URIs and add a level of 
>> indirection between them (I think this has been mentioned before).
> 
> 
> The DNS is designed to solve exactly this problem. Using IPs in RDF 
> statements is asking for trouble, IMO. I don't think you have to go all 
> the way to URNs to avoid this.
> 

What I'm trying to demonstrate is that there's a difference between how 
you access the model and the name of the model.  Host names and IP 
addresses are just one of the things that can change through the life of 
the data.

Another example, you name an SQL table "employee", you may access it 
through JDBC, EJBs, and an HTTP interface.  Each of these three ways of 
accessing the same data have different URIs but it's the same data.  Any 
queries or code which accesses the data uses the same name in the FROM 
clause (or equivalent).

I don't see how blank nodes are appropriate for naming graphs in this 
way.  You can't share a blank node around a network - it's a global name 
- not something that is local to a graph.
Received on Sunday, 12 September 2004 23:08:04 GMT

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