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Re: Permanent model names in TKS/Kowari

From: Dan Connolly <connolly@w3.org>
Date: Sat, 20 Nov 2004 22:21:06 -0600
To: Tom Adams <tom@tucanatech.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1101010867.27188.87.camel@dirk>
On Sat, 2004-11-20 at 23:04 -0500, Tom Adams wrote:
> Hi guys,
> 
> Here is a summary of the discussions that we've been having internally 
> on permanent model names

There's that "model" word again... would you please rephrase
in Feb 2004 terminology? Do you mean RDF Graph?
http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#dfn-rdf-graph

or do you mean something mutable? (Graphs are immutable syntactic
things, like numerals and strings).

>  and ideas for a) how we name models and b) how 
> we separate model names from their access mechanism, there's also some 
> syntax at the bottom. For the record, a most of this discussion comes 
> from Andrew Newman. All comments are speculation, I don't believe we've 
> implemented these ideas as yet ;)
> 
> Our discussions have been motivated by a number of reasons, a lot of 
> which have been coming to us from customers:
> 
> o Models should to be named in order to be able to reference them in 
> queries;
> o Names should be independent of the method of access (i.e. protocol);

Not if you mean "model" in the sense of "mutable store" ala
"file" or "document".

And if you mean something immutable, it seems a lot simpler to use
a hash.

> o Names should be independent of the hostname of the machine they're 
> stored on;

Yes, but DNS names meet that criterium. (hint: which machine
is www.w3.org? Which continent, for that matter? A: many.)

> o Models should be able to be moved from machine to machine;
> o The content of a model may reside in a different storage mechanism 
> over time, e.g. RDF/XML file or TKS/Kowari model.
> 
> Some other work has been done around similar things. @semantics did a 
> presentation on resolving models at the WWW2004 conference:
> 
> http://www.asemantics.com/presos/devdays-2004/y-532x400-12.html
> 
> There's a few RFCs that cover similar topics:
> 
> DDDS part 3: http://www.ietf.org/rfc/rfc3403.txt
> DDDS part 4: http://www.ietf.org/rfc/rfc3404.txt
> Using HTTP in URN Resolution: http://www.ietf.org/rfc/rfc2169.txt
> Handle System Overview: http://www.ietf.org/rfc/rfc3650.txt
> 
> So cutting to the crunch, TKS/Kowari currently use model names of the 
> form:
> 
> protocol://hostname/servername#modelname
> 
> For example:
> 
> rmi://knuth.bne.tucanatech.com/server1#foo
> beep://knuth.bne.tucanatech.com/server1#foo
> 
> This confuses two distinct properties of a model: the model name and 
> how to access the model.

I'm not at all sure that's the case.

> TKS/Kowari stores model information in a special place called the 
> system model. This model stores information such as the type of a 
> model, e.g. a full text model or a native "Tucana" model. As far as 
> Tucana is concerned, we want to solve the problems outlined above, but 
> also allow for backwards compatibility with existing queries. As we 
> want to be able to store model information in RDF, and make statements 
> about models, we need to use a resource to reference a model. We're 
> considering using URNs to name models.
> 
> Our proposed new model naming scheme would use the system model to 
> contain information about the models including their name and how to 
> access them. So for example we could be storing the following triples:
> 
> <urn:slashdot-org:news-rss> <access> <http://slashdot.org/news.rss>
> <urn:slashdot-org:news-rss> <updateEvery> <5 minutes>
> <urn:knuth-com:server1:foo> <access> <rmi://localhost/server1>
> <urn:tucanatech-com:server1:hr> <access> <rmi://localhost/server1>

Why not
  <http://example/someplace#slashdotNews> <access> ...
?


> The first model <urn:slashdot-org:news.rss> is an remote model that you 
> access using the given URL (http://slashdot.org/news.rss) and you 
> update it every 5 minutes.

Aha... so you _do_ mean something mutable.

>  The second and third models are local 
> models. The third model is a company model that you just happen to have 
> a local copy of.
> 
> So now onto some syntax examples, feel free to tune out.

Please take a look at

  The Myth of Names and Addresses
  http://www.w3.org/DesignIssues/NameMyth

and see if you still think urn: helps at all.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E

Received on Sunday, 21 November 2004 04:20:24 GMT

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