- From: Orri Erling <erling@xs4all.nl>
- Date: Wed, 25 Mar 2009 14:25:20 +0100
- To: "'Simon Schenk'" <sschenk@uni-koblenz.de>, <public-rdf-dawg@w3.org>
- Cc: "'SPARQL Working Group'" <public-rdf-dawg@w3.org>
-----Original Message----- From: public-rdf-dawg-request@w3.org [mailto:public-rdf-dawg-request@w3.org] On Behalf Of Simon Schenk Sent: Wednesday, March 25, 2009 1:38 PM To: public-rdf-dawg@w3.org Cc: 'SPARQL Working Group' Subject: Re: On Parameters > In all SQL CLI's (call level interface) this is a given. Also, most > CLI's have array parameters, i.e. passing multiple sets of parameter > bindings in a single client-server message. The array parameter > question can be addressed in the conntext of the SPARQL protocol by > the HTTP 1.1 pipelining Apart from query optimization I see an interesting application for arrays in federation. Eric proposed something similar for this purpose [1]. Without it, distributed joins either need a large number of separate queries (resulting in high latency), or you need to mimic [1] by rewriting the query with lots of FILTERs or UNIONs as proposed in [2], which is a rather hacky solution. Cheers, Simon [1] http://www.w3.org/2007/05/SPARQLfed/ [2] Zemanek, Jan, Schenk, Simon, and Svatek, Vojtech. Optimizing SPARQL Queries over Disparate RDF Data Sources through Distributed Semi-Joins. ISWC 2008 Poster and Demo Session Proceedings. CEUR-WS. 2008. Simon Quite right. I would propose to support a POST request with an XML body for parameter rows and a corresponding wrapper format for keeping the result sets separated. Easy to specify and easy to implement. I am quite uncertain of the committee's adoption of such a thing, though, as parameters themselves are not a given. It is also true that a similar effect to array parameters can be had with a pipelined HTTP request: Write all the request headers and then read all the responses. If the query itself is kept around for the next request, it can be reused from a cache of recently compiled queries. Putting or's into a query for federation is not really desirable, to be sure. Orri
Received on Wednesday, 25 March 2009 13:26:08 UTC