- From: Steve Harris <steve.harris@garlik.com>
- Date: Thu, 30 Sep 2010 12:47:06 +0100
- To: Andy Seaborne <andy.seaborne@epimorphics.com>
- Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
On 2010-09-30, at 11:57, Andy Seaborne wrote:
> Following a jena-dev question, I wondered what do implementations do with the following?
>
> # Duplicate select variable - SPARQL 1.0
> SELECT ?s ?s ?p ?o
> {
> ?s ?p ?o
> }
4store only returns each column once, but issues a warning:
# 4s-query test 'SELECT ?s ?p ?o ?s WHERE { ?s ?p ?o } LIMIT 1'
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="s"/>
<variable name="p"/>
<variable name="o"/>
</head>
<!-- parser warning: Variable s duplicated in SELECT at line 1 -->
<results>
<result>
<binding name="s"><uri>file:///tmp/c</uri></binding>
<binding name="p"><uri>file:///tmp/d</uri></binding>
<binding name="o"><literal datatype="http://www.w3.org/2001/XMLSchema#integer">5</literal></binding>
</result>
</results>
</sparql>
5store duplicates the column, and no warning:
# keep-query testkb-swh -f sparql 'SELECT ?s ?p ?o ?s WHERE { ?s ?p ?o } LIMIT 1'
<?xml version="1.0"?>
<sparql xmlns="http://www.w3.org/2005/sparql-results#">
<head>
<variable name="s"/>
<variable name="p"/>
<variable name="o"/>
<variable name="s"/>
</head>
<results>
<result>
<binding name="s"><uri>test:x</uri></binding>
<binding name="p"><uri>test:y</uri></binding>
<binding name="o"><literal>ntriples</literal></binding>
<binding name="s"><uri>test:x</uri></binding>
</result>
</results></sparql>
- Steve
--
Steve Harris, CTO, Garlik Limited
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Received on Thursday, 30 September 2010 11:48:13 UTC