W3C home > Mailing lists > Public > www-rdf-rules@w3.org > January 2005

RE: Brackets and Clark Notation in SPARQL

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Tue, 4 Jan 2005 11:54:34 -0000
Message-ID: <8D5B24B83C6A2E4B9E7EE5FA82627DC960115A@sdcexcea01.emea.cpqcorp.net>
To: "James Cerra" <jfcst24_public@yahoo.com>, <www-rdf-rules@w3.org>


-------- Original Message --------
> From: James Cerra <>
> Date: 21 December 2004 04:20
> 
> Right now, SPARQL uses less-than and greater-than
> brackets to identify a URI.  This is probably due to
> the influence of N3 and Jena's RDQL.  So they are
> shown as:
> 
> <http://example.com/uri>

It goes back further - see the discussion in section 2.4.3 of RFC 2396.
N-Triples does the same.

> However, this is hard to write in XML, since every
> less-than sign should be escaped.  

Unfortunately true.  CDATA can help.  Using the PREFIX mechanism can
reduce the number of <>.

> Therefore, I think
> SPARQL should use Clark Notation [1] to represent
> them.  That is:
> 
> {http://example.com/uri}
> 
> or even:
> 
> {http://example.com/}uri
> 
> I don't know whether the second form should be allowed
> or not.

In Clark Notation that is namespace http://example.com/, local part uri.
It's RDF that makes the tranlsation to the concatenated URI
http://example.com/uri

> 
> Now I am aware that the WG wants to use curly-brackets
> where it currently uses parentheses [2].  However
> there doesn't seem to be a particular reason given for
> the change.  Why change what already works?

{} is used in languages like N3 for grouping. The same argument of usage
elsewhere suggests using them for the same in SPARQL.  There are not
enough delimiter pairs in the world!  Parentheses are already overloaded
for triples, and expressions like 3*(?x+1).

	Andy

> 
> --
> Jimmy Cerra
> 
> [1] http://www.jclark.com/xml/xmlns.htm
> 
> [2] http://www.w3.org/TR/rdf-sparql-query/#NestedPatterns












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Received on Tuesday, 4 January 2005 11:55:08 GMT

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