Hoi,

Sorry for being dense.. What is wrong with there being no value ? Having a "no value" is imho understanding only a complication of saying nothing... Why not say nothing in the first place ?

Thanks,

     GerardM

On 22 April 2015 at 21:52, Markus Krötzsch <markus@semantic-mediawiki.org> wrote:

Hi Thomas,

On 22.04.2015 20:06, Thomas Douillard wrote:

Hi, there is items about Wikibase data model in Wikidata (created by me,
but not only)

If I understand correctly, they could be cited in the semantic web as
https://www.wikidata.org/entity/Q19798647

"No value" is exactly that: not a value. It should not be confused with a (definite) value that is used with claims (as the item description seems to suggest). The reason why we introduced "no value" was to be able to say this without resorting to a "special value" to represent this.

You can also find some rationale about this in our article "Wikidata: a free collaborative knowledgebase" (see https://ddll.inf.tu-dresden.de/web/Article4002/en). Basically, the main point is that, if you are querying for two people with a common child, you wouldn't want to get pairs of people who both have "novalue" as a value for "child". The same is true for "some value" (sometimes referred to as "unknown value") -- again, if this would be a definite "special" value, and be treated like a value in queries, it would lead to wrong results.

Cheers,

Markus

(If they are kept /o\)

Tom²


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