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RE: Another attempt...

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 24 Mar 2008 21:34:21 +0000
To: Andrew Newman <andrewfnewman@gmail.com>
CC: "public-rdf-dawg-comments@w3.org" <public-rdf-dawg-comments@w3.org>
Message-ID: <38CBA1F6A350B044AF785E63AAC3C677646E21E64C@G5W0276.americas.hpqcorp.net>
Andrew,

> Test 2
> =====
> Data:
> http://www.w3.org/2001/sw/DataAccess/tests/data-r2/graph/data-g1.ttl

>
> Query:
> SELECT * WHERE { ?s ?p ?o UNION {} }

Did you mean:
{ { ?s ?p ?o } UNION {} }

>
> Results (this is suppose to represent empty):
>
> <?xml version="1.0"?>
> <sparql
>    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>    xmlns:xs="http://www.w3.org/2001/XMLSchema#"
>    xmlns="http://www.w3.org/2005/sparql-results#" > <head>
>   <variable name="s"/>
>   <variable name="p"/>
>   <variable name="o"/>
> </head>
>   <results>
>     <result>
>     </result>
>  </results>
> </sparql>

In [2008Mar/0013] there is a complete worked example with "UNION {}" and it shows how the results are obtained by referencing the SPARQL specification at each step.  The purpose of the example in [2008Mar/0013] is so we can find the first point of difference or first point where pre-requisite knowledge [2008Mar/0029] is used.

In [2008Mar/0015] you said of that example:
"""
It simple to evaluate you don't need any
steps if you are UNIONing the identity for JOIN.
"""

I can't find mention of this - which text in the definition of the evaluation of UNION does this refer to?  (For quick reference: the specification gives the definition for union of two solution multi-sets at [1]; the join identity is the multiset {{}}, cardinality 1. (sec 12.3) - I can work through that point if that would help.)


If you are raising a test case against the text of the specification, could you work through the example in [2008Mar/0013] so we can identify the step or steps where you differ from the description in that message.


If you are raising a test case against the design of SPARQL, this has been addressed in Lee's message [2008Mar/0025].

        Andy

[1] http://www.w3.org/TR/rdf-sparql-query/#defn_algUnion

[2008Mar/0013] http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2008Mar/0013

[2008Mar/0015] http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2008Mar/0015

[2008Mar/0029] http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2008Mar/0029

[2008Mar/0025] http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2008Mar/0025

Received on Monday, 24 March 2008 21:35:52 GMT

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