Re: Inequality and type errors

Hi Marcel,

It is the FILTER overall that treats treats errors as false - not the 
operator, not that it matters much here.

open-eq-08 is making some other assumptions:

It is using the fact that literals, URIs and blanknodes are disjoint as 
values in an expression.  :xyz can't not be value-equal to "xyz".

The manifest entry for this test has some additional data (there ought 
to be more):

:open-eq-08 a mf:QueryEvaluationTest ;
     ...
     mf:requires mf:StringSimpleLiteralCmp ;
     mf:requires mf:LangTagAwareness ;
     mf:requires mf:KnownTypesDefault2Neq ;
     mf:notable  mf:IllFormedLiteral ;
     ...

With langtag awareness (otherwise a processor will throw error on 
encountering one as a FILTER value):

| :x2 | "xyz"@en           | :x8 | :xyz               |

this is SPARQL 1.0 so the test uses RDF 1.0 - lang tag literals do not 
have a datatype and the notion of "value" isn't really that precise.The 
test assumes that simple strings (no datatype , no lang tag) and 
literals with lang tag are disjoint so:

| :x3 | "xyz"@EN           | :x1 | "xyz"              |

In
https://www.w3.org/2001/sw/DataAccess/tests/README
says that mf:KnownTypesDefault2Neq allows for the processor to know that 
there are disjoint values spaces: e.g. an xsd:integer but the terms 
using ^^xsd:integer are illegal lexical forms so don't have an integer 
value.

     Hope that helps, at least in part,
     Andy

On 27/10/2018 17:08, Marcel Otto wrote:
> Hi.
> 
> Some of the open-world tests fail on my SPARQL implementation in Elixir [1]. These tests seem to suggest that the != operator should treat type errors as false, although there's no hint on this behaviour in the spec. For example, the open-eq-08 test states that the result for this query:
> 
> PREFIX : <http://example/>
> PREFIX  xsd: <http://www.w3.org/2001/XMLSchema#>
> SELECT *
> {
>      ?x1 :p ?v1 .
>      ?x2 :p ?v2 .
>      FILTER ( ?v1 != ?v2 )
> }
> 
> over this data:
> 
> @prefix : <http://example/> .
> @prefix  xsd: <http://www.w3.org/2001/XMLSchema#> .
> :x1 :p "xyz" .
> :x2 :p "xyz"@en .
> :x3 :p "xyz"@EN .
> :x4 :p "xyz"^^xsd:string .
> :x5 :p "xyz"^^xsd:integer .
> :x6 :p "xyz"^^:unknown .
> :x7 :p _:xyz .
> :x8 :p :xyz .
> 
> should include almost all permutations. I'm not seeing how this behavior can be explained with the spec, which defines != as the fn:not negation of the respective equality comparison according to the types. The equality comparisons are defined to result in almost all cases with different types in a type error. With fn:not defined to produce an error if its argument is an error, all the inequality comparisons in this example should result in a rejection of the solution, which my implementation exactly does.
> 
> Kind regards
> Marcel Otto
> 
> 
> [1]: https://github.com/marcelotto/sparql-ex
> 
>

Received on Monday, 29 October 2018 10:18:59 UTC