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Re: [TTL] Differences between SPARQL and Turtle.

From: Eric Prud'hommeaux <eric@w3.org>
Date: Sat, 23 Apr 2011 15:27:41 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Cc: public-rdf-wg@w3.org
Message-ID: <20110423192739.GA3342@w3.org>
* Andy Seaborne <andy.seaborne@epimorphics.com> [2011-04-23 17:33+0100]
> (resent with note of ISSUE-1 for trackbot)
> 
> RDF-WG ISSUE-1
> http://www.w3.org/2011/rdf-wg/track/issues/1
> 
> 
> I've gathered the differences together into a live document
> 
> http://www.w3.org/2011/rdf-wg/wiki/Diff_SPARQL_Turtle#Relevant_RDF_WG_Decisions
> 
> 
> And added a new one: Turtle and SPARQL treat \u escape processing
> differently because they happen at different times in the parsing process.

+1

I've had a hard time defending the fact that one can't simply escape
characters in PNames (SPARQL's QNames). This comes up in DB dumps, e.g.

  PREFIX p: <http://foo.example/db/People#> .
  SELECT ?who ?dept WHERE {
    ?who p:deptName\u002CdeptCity ?dept
  }

SPARQL says \u002C is substituted with ',' *before* parsing (and ','
isn't valid in local names).

We could potentially simplify the story for Turtle users by adding
unicode escape sequences (I called them UCHARs) to qnames. I hacked
this up in a grammar called turtleEsc http://w3.org/brief/MjM0 . It
validates strings like:

  @prefix α: <http://foo.example/bar#> .
  <ab\u00E9xy> \u03B1:p "ab\u0022cd" .

and is, IMO, pretty easy to explain to users. The downside is that
we lose grammar control over folks adding chars like [<> ] to IRIs
(i.e. left to semantic validation) but I believe it's still better
than making PNames un-escapable.


> 	Andy
> 
> 

-- 
-ericP
Received on Saturday, 23 April 2011 19:28:11 GMT

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