On 16/04/16 07:23, Michael Schmidt wrote:
Dear community,
we’ve got a question regarding the semantics of FILTER NOT IN (inspired
by
http://www.w3.org/2001/sw/DataAccess/tests/data-r2/syntax-sparql1/manifest#sparql11-not-in-02),
which boils down to literal equality issues.
I don't see that test in that manifest.
Also,
syntax-sparql1
Those are syntax tests, not evaluation tests.
In that manifest, all tests are "#syntax-...."
Look at the following example:
- Data: <http://s> <http://p> "a” .
- Query:
SELECT * WHERE {
?s ?p ?o
FILTER (?o NOT IN (1))
}
According to the standard ("The |NOT IN| operator is equivalent to the
SPARQL expression: (lhs != expression1) && (lhs != expression2) && …)”)
this query is equivalent to:
SELECT * WHERE {
?s ?p ?o
FILTER (?o!=1)
}
Further, the standard says "The test is done with "!=" operator, which
tests for not the same value, as determined by the operator mapping
<https://www.w3.org/TR/sparql11-query/#OperatorMapping>.”, where the
operator mapping section defines no explicit rule for comparing plain
literals to numerics (but delegates to various casting/substitution
rules defined in XPath standards) .
My questions now are:
- What is the expected result of “a”!=1? And why — which of the rules in
the operator mapping table would apply here (if any?). The expected
result of sparql11-not-in-02 indicates that this neq comparison should
evaluate to true rather than error, but I actually do not see why.
There is no implicit casting in SPARQL.
If there is no mapping then it is a evaluation error.
(specific engines may do better - for example the value space of strings
and the value space of integers don't overlap so the answer is "false")
- Would the result be different in the context of RDF1.1, where wecwould
compare “a”^^xsd:string!=1 instead?
No.
Thanks in advance for any help,
Michael
Andy
PS You may be interested in the community work to maintain the RDF 1.1
and SPARQL 1.1 tests:
https://www.w3.org/community/rdf-tests/
https://github.com/w3c/rdf-tests
