On 19.08.2014 12:20, Gerard Meijssen wrote:

Hoi,
I cannot parse this ..

What Thomas is saying is that classification (putting things into "categories") and querying (finding things based on certain properties) can be combined in a natural way. In ontology languages like OWL, you can make statements that say, roughly speaking, that "all results of query A belong to class B". This allows you to build a classification partly automatically, and to ensure that your classification is always consistent with your data.

>From this perspective, you can view Wikidata's stored queries as similar to OWL's class expressions in that they allow you to define classes based on the data given for each item, without having to go through all the items to add classes manually. What Thomas is referring to is of course slightly more advanced still, but maybe this clarifies part of the idea.

Cheers,

Markus

On 19 August 2014 11:43, Thomas Douillard <thomas.douillard@gmail.com

<mailto:thomas.douillard@gmail.com>> wrote:

    Note that in Wikidata we are developping methods and tools to class
    items in « classes », which in short are sets of real world things
    or events. In languages like the w3c language and standards OWL2

    <https://en.wikipedia.org/wiki/OWL2>. In this language you can

    assign a class to an element (a media in the common case) to a class
    (that can be seen as a better defined category) either by creating a
    statement « this media belongs to that category » (in Wikidata this
    is done by using the « instance of » property

    <https://www.wikidata.org/wiki/Property:P31>) or by associating a so

    called «class expression» in OWL (an analog of a query but more
    powerful) Then in OWL any item who satisfy the criteria of the query
    or class expression associated to a class belongs to that class
    without stating it explicitely.  In short, the possibility to assign
    an arbitrary class to an item when a query is not enough will also
    be possible with just a metadata repository, we may in the future
    even be able to mix these two ways to class medias.


    2014-08-19 10:14 GMT+02:00 James Heald <j.heald@ucl.ac.uk

    <mailto:j.heald@ucl.ac.uk>>:

        Also there might be queries one might want to run on the
        categories, which would be another reason to include them in
        Commons Wikibase.

           -- J.



        On 19/08/2014 07:00, Gerard Meijssen wrote:

            Hoi,
            I know the categories in Commons exist. I also know that you
            do not have to
            add categories when an image is uploaded. Many people do not
            consider the
            categories because they are just there and are not easy nor
            obvious without
            a long study.

            They are there and they evolve. When the "community" finds
            that they are no
            longer useful, there will be others who still want to work
            on it. They can,
            it is a harmless occupation. Why would we consider removing
            category
            structures as long as someone cares about them ??
            Thanks,
                     GerardM

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