good evening;
> On 2016-01-30, at 17:47, Andy Seaborne <a...@apache.org> wrote:
>
> On 30/01/16 14:24, Jörn Hees wrote:
>> Hi,
>>
>>> What was RDFLib producing?
>>
>> VALUES (?x ?ys ?zs) {
>> (3 UNDEF 15)
>> (5 UNDEF 25)
>> (2 6 UNDEF)
>> }
>>
>>
>>> Both are right, though the Virtuoso one is pragmatically more useful in
>>> this specific case. There is no one "right" in general when SAMPLE is
>>> involved. Aggregation calculation retains errors and ?z of UNDEF is an
>>> error. SAMPLE picks any value from the choices, and at that point, errors
>>> are "values". See ListEval.
>>
>> I understand that sample can pick an arbitrary value from its choices.
>> When it comes to error cases though, it seems this causes confusion as
>> people might not expect an UNDEF to be a solution if there are other values
>> to pick from... (undef has to be picked: (5 UNDEF 25) vs. can pick an actual
>> value: (2 6 10)).
>>
>> As you put it yourself it's pragmatically more useful, so would it hurt to
>> put a preference like that into the standard?
>
> The v1.1 standard is now fixed - but good suggestion for a prospective
> change. I've added it to the errata document, linked to your report, which
> is the best I can do.
>
> https://www.w3.org/2013/sparql-errata#errata-query-16
>
> Changing the recommended behaviour of systems, even if "better", was
> something the 1.1 WG was loath to do, and chartered not to in the case of
> SPARQL 1.0 -> 1.1. In other words, any system that has faithfully
> implemented the standard up to now should be respected and not be impacted.
>
> In the meantime, getting the implementations to agree is the way forward. If
> that choice is the same everywhere, then it is a better case for future
> errata/clarification.
this would do well to go into the regression tests as a test profile parameter
and service description property.
>
> I have raised JENA-1126 for Jena and proposed a change to pick a defined
> value.
>
> Thanks
> Andy
>
>> In any case it would be cool if there was a small example (like the one
>> above) that clarifies the behaviour.
>>
>> Jörn
>
>
> [JENA-1126]
> https://issues.apache.org/jira/browse/JENA-1126
>
>
---
james anderson | ja...@dydra.com | http://dydra.com
