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Re: Comment: don't use ? and $. Pick one. [OK?]

From: Dan Connolly <connolly@w3.org>
Date: Mon, 06 Mar 2006 08:29:47 -0600
To: Elliotte Harold <elharo@metalab.unc.edu>
Cc: Pat Hayes <phayes@ihmc.us>, public-rdf-dawg-comments@w3.org
Message-Id: <1141655387.26363.1165.camel@dirk.w3.org>

On Mon, 2006-03-06 at 06:37 -0500, Elliotte Harold wrote:
> Pat Hayes wrote:
> >> On Sun, 2006-03-05 at 18:56 -0500, Elliotte Harold wrote:
> >>>  If there's a justification for using both $ and ? to represent
> >>>  variables, I haven't found it yet.
> >>
> >> The WG made that choice in the course of resolving the
> >> punctuationSyntax issue.
> >>  http://www.w3.org/2001/sw/DataAccess/issues#punctuationSyntax
> 
> I may not be following the right link, but I don't see the connection. 
> Is there a reference in the archives other than the below?

The punctuation syntax issue collects a number of syntactic details
about how queries are punctuated, including variable name syntax.


> >> A number of design considerations were laid out in:
> >> Draft: open issues around '?' use.
> >> http://lists.w3.org/Archives/Public/public-rdf-dawg/2004OctDec/0160
> 
> I think this makes some good arguments for using a $ instead of a ?. 
> However it doesn't convince me that using both is a good idea. Why are 
> two characters considered necessary here? Why not just pick the $ and be 
> done with it?

The use of ?var syntax in SPARQL goes back all the way to the 1st
WD in October 2004
 http://www.w3.org/TR/2004/WD-rdf-sparql-query-20041012/

The number of reviewers, users, and implementors that we would need
to collaborate with in order to take ?var out is considerable, and
it's not clear that we have an argument that is sufficient to convince
them. True, allowing both adds various costs, but this is largely
sunk cost. The details of the specification are worked out; we have
test cases and multiple implementations. A growing number of users
have learned the ?var syntax, and those that need to use ODBC-style
systems seem to know about and be happy with $var.
It seems unlikely that we would get consensus around a change
to take out ?var or $var in a reasonable amount of time, and the
number of parties that are interested to see SPARQL advance to
Candidate Rec soon is considerable.


Again, please let us know whether you find this response satisfactory.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Monday, 6 March 2006 14:30:21 GMT

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