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Re: Small items for SPARQL

From: Dan Connolly <connolly@w3.org>
Date: Fri, 17 Dec 2004 13:59:43 -0600
To: andy.seaborne@hp.com
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1103313583.3082.269.camel@dirk>

On Fri, 2004-12-17 at 17:56 +0000, Seaborne, Andy wrote:
> 1/ Character sets
> 
> I propose SPARQL queries use UTF-8

SPARQL queries are sequences of characters; how they're
encoded is a protocol issue, right?

i.e. under the "chair expects editor to respond to each
proposal to change that editor's spec; others in the
WG are welcome to advise; chair steps in if consensus
does not emerge" sort of game, I'm watching for Kendall's response.

> This allows multi (natural) language queries.
> 
> HTTP GET will have to encoded as usual - we do need to decide the string being
> encoded.
> 
> In HTTP POST, Content-Type applies to the entity body.
> A request sent by HTTP POST may use Content-Type to change the charset.
> 
> Experiences with declaring the charset in the content show
> this to be very error prone:
> 
>        a/ it may disagree with the HTTP header
> 
>        b/ once opened in one fashion, say the default platform charset,
>           it can be hard to reopen in another fashion: the underlying
>           stream maybe buffered.
> 
> Aside: as the syntax currently stands (a keyword must be first), it is possible
> to snoop and tell the difference between UTF-8 and UTF-16.
> 
> 
> 2/ We will need a URI for SPARQL

I'm not so sure.

My implementation experience suggests we choose
a URI for the relationship between
a KB and a SPARQL query for that KB.

> Suggestions:
> http://www.w3.org/2001/sw/DataAccess/SPARQL
> 
> (We might want to allow for future revisions but I assume a new WG would have a 
> new URI itself so versioning isn't needed here).
> 
> 
> 3/ Relative URIs
> 
> Queries would need a base URI to resolve any relative URIs.

would... subjunctive... 

is this an issue in the current draft?

I can't tell from the grammar...
  http://www.w3.org/2001/sw/DataAccess/rq23/#term-sparql-URI
  $Revision: 1.160 $ of $Date: 2004/12/17 18:16:17 $

I suggest uriRef as the terminal name, if relative URI references
are, by intent, allowed.

Hmm... we don't currently specify how the syntactic productions
relate to the formal definitions, do we?


> We can either say "no relative URIs" (that might makes the tests harder if we 
> follow the style of the manifests in using relative URIs).
> 
> For the protocol, "query-uri=" is a natural default base but there isn't a 
> natural one in all situations like local queries from a program or one sent as 
> plain "query="
> 
> I suggest a BASE clause in the QL that must be before PREFIXes.  It takes a 
> single, <> quoted URI. It is not required in every query.

Seems reasonable.

> 	Andy

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Friday, 17 December 2004 19:59:25 GMT

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