Except that there are lots of people who have appeared in one movie who don't consider themselves actors and should not have the 'occupation=>actor/actress'. There are good reasons for some constraints to be gadgets that can be overridden rather than hard coded semantic limits.
I do think we should be able to have hard coded reverse properties and symmettric properties. Joe filceolaire On Wed, May 14, 2014 at 2:33 PM, Markus Krötzsch < mar...@semantic-mediawiki.org> wrote: > Hi Eric, > > Thanks for all the information. This was very helpful. I only get to > answer now since we have been quite busy building RDF exports for Wikidata > (and writing a paper about it). I will soon announce this here (we still > need to fix a few details). > > You were asking about using these properties like rdfs:subClassOf and > rdf:type. I think that's entirely possible, since the modelling is very > reasonable and would probably yield good results. Our reasoner ELK could > easily handle the class hierarchy in terms of size, but you don't really > need such a highly optimized tool for this as long as you only have > subClassOf. In fact, the page you linked to shows that it is perfectly > possible to compute the class hierarchy with Wikidata Query and to display > all of it on one page. ELK's main task is to compute class hierarchies for > more complicated ontologies, which we do not have yet. OTOH, query > answering and data access are different tasks that ELK is not really > intended for (although it could do some of this as well). > > Regarding future perspectives: one thing that we have also done is to > extract OWL axioms from property constraint templates on Wikidata talk > pages (we will publish the result soon, when announcing the rest). This > gives you only some specific types of OWL axioms, but it is making things a > bit more interesting already. In particular, there are some constraints > that tell you that an item should have a certain class, so this is > something you could reason with. However, the current property constraint > system does not work too well for stating axioms that are not related to a > particular property (such as: "Every [instance of] person who appears as an > actor in some film should be [instance of] in the class 'actor'" -- which > property or item page should this be stated on?). But the constraints show > that it makes sense to express such information somehow. > > In the end, however, the real use of OWL (and similar ontology languages) > is to remove the need for making everything explicit. That is, instead of > "constraints" (which say: "if your data looks like X, then your data should > also include Y") you have "axioms" (which say: "if your data looks like X, > then Y follows automatically"). So this allows you to remove redundancy > rather than to detect omissions. This would make more sense with "derived" > notions that one does not want to store in the database, but which make > sense for queries (like "grandmother"). > > One would need a bit more infrastructure for this; in particular, one > would need to define "grandmother" (with labels in many languages) even if > one does not want to use it as a property but only in queries. Maybe one > could have a separate Wikibase installation for defining such derived > notions without needing to change Wikidata? There are no statements on > properties yet, but one could also use item pages to define derived > properties when using another site ... > > Best regards, > > Markus > > P.S. Thanks for all the work on the "semantic" modelling aspects of > Wikidata. I have seen that you have done a lot in the discussions to > clarify things there. > > > > On 06/05/14 04:53, emw wrote: > >> Hi Markus, >> >> You asked "who is creating all these [subclass of] statements and how is >> this done?" >> >> The class hierarchy in >> http://tools.wmflabs.org/wikidata-todo/tree.html?q=Q35120&rp=279&lang=en >> shows a few relatively large subclass trees for specialist domains, >> including molecular biology and mineralogy. The several thousand >> subclass of 'gene' and 'protein' subclass claims were created by members >> of WikiProject Molecular biology (WD:MB), based on discussions in [1] >> and [2]. The decision to use P279 instead of P31 there was based on the >> fact that the "is-a" relation in Gene Ontology maps to rdfs:subClassOf, >> which P279 is based on. The claims were added by a bot [3], with input >> from WD:MB members. The data ultimately comes from external biological >> databases. >> >> A glance at the mineralogy class hierarchy indicates it has been >> constructed by WikiProject Mineralogy [4] members through non-bot >> edits. I imagine most of the other subclass of claims are done manually >> or semi-automatically outside specific Wikiproject efforts. In other >> words, I think most of the other P279 claims are added by Wikidata users >> going into the UI and building usually-reasonable concept hierarchies on >> domains they're interested in. I've worked on constructing class >> hierarchies for health problems (e.g. diseases and injuries) [5] and >> medical procedures [6] based on classifications like ICD-10 and >> assertions and templates on Wikipedia (e.g. [8]). >> >> It's not incredibly surprising to me that Wikidata has about 36,000 >> subclass of (P279) claims [9]. The property has been around for over a >> year and is a regular topic of discussion [10] along with instance of >> (P31), which has over 6,600,000 claims. >> >> You noted a dubious claim subclass of claim for 'House of Staufen' >> (Q130875). I agree that instance of would probably be the better >> membership property to use there. Such questionable usage of P279 is >> probably uncommon, but definitely not singular. The dynasty class >> hierarchy shows 13 dubious cases at the moment [11]. I would guess less >> than 5% of subclass of claims have that kind of issue, where instance of >> would make more sense. I think there are probably vastly more cases of >> the converse: instance of being used where subclass of would make more >> sense. >> >> As you probably know, P31 and P279 are intended to have the semantics of >> rdf:type and rdfs:subClassOf per community decision. A while ago I read >> a bit about the ELK reasoner you were involved with [12], which makes >> use of the seemingly class-centric OWL EL profile. Do you have any >> plans to integrate features of ELK with the Wikidata Toolkit [13]? How >> do you see reasoning engines using P31 and P279 in the future, if at all? >> >> Thanks, >> Eric >> >> https://www.wikidata.org/wiki/User:Emw >> >> [1] >> https://www.wikidata.org/wiki/WT:MB#Distinguishing_between_ >> genes_and_proteins >> [2] https://www.wikidata.org/wiki/WT:MB#Human.2Fmouse.2F..._ID >> [3] https://www.wikidata.org/wiki/User:ProteinBoxBot. Chinmay Nalk >> (https://www.wikidata.org/wiki/User:Chinmay26) did all the work on this, >> with input from WD:MB. >> [4] https://www.wikidata.org/wiki/Wikidata:WikiProject_Mineralogy >> [5] >> http://tools.wmflabs.org/wikidata-todo/tree.html?q= >> Q15281399&rp=279&lang=en >> [6] >> http://tools.wmflabs.org/wikidata-todo/tree.html?q=Q796194&rp=279&lang=en >> [7] http://apps.who.int/classifications/icd10/browse/2010/en >> [8] https://en.wikipedia.org/wiki/Template:Surgeries >> [9] >> https://www.wikidata.org/w/index.php?title=Wikidata: >> Database_reports/Popular_properties&oldid=125595374 >> [10] Examples include >> - https://www.wikidata.org/wiki/Wikidata:Project_chat#chemical_element >> - >> https://www.wikidata.org/wiki/Wikidata:Project_chat/Archive/ >> 2013/12#Top_of_the_subclass_tree >> >> - >> https://www.wikidata.org/wiki/Wikidata:Project_chat/Archive/ >> 2014/01#Question_about_classes.2C_and_.27instance_of.27_vs_.27subclass.27 >> [11] >> http://tools.wmflabs.org/wikidata-todo/tree.html?q=Q164950&rp=279&lang=en >> [12] http://korrekt.org/page/The_Incredible_ELK >> [13] https://www.mediawiki.org/wiki/Wikidata_Toolkit >> >> >> On Mon, May 5, 2014 at 12:46 PM, Markus Kroetzsch >> <markus.kroetz...@tu-dresden.de <mailto:markus.kroetz...@tu-dresden.de>> >> >> wrote: >> >> Hi, >> >> I got interested in subclass of (P279) and instance of (P31) >> statements recently. I was surprised by two things: >> >> (1) There are quite a lot of subclass of statements: tenth of >> thousands. >> (2) Many of them make a lot of sense, and (in particular) are not >> (obvious) copies of Wikipedia categories. >> >> My big question is: who is creating all these statements and how is >> this done? It seems too much data to be created manually, but I >> don't see obvious automated approaches either (and there are usually >> no references given). >> >> I also found some rare issues. "A subclass of B" should be read as >> "Every A is also a B". For example, we have "Every piano (Q5994) is >> also a keyboard instrument (Q52954)". Overall, the great majority of >> cases I looked at had remarkably sane modelling (which reinforces my >> big question). >> >> But there are still cases where "subclass of" is mixed up with >> "instance of". For example, Wikidata also says "Every 'House of >> Staufen' (Q130875) is also a dynasty (Q164950)". This is dubious -- >> how many instances of 'House of Staufen' are there? I guess we >> really want to say that "The House of Staufen is a(n instance of) >> dynasty." Is this a singular error or a systematic issue? >> >> I guess there is already a group of people who deal with such issues >> -- or it would be a miracle that things are in such a good shape >> already :-) I have read the talk page for subclass of, but that does >> not seem to explain the original of all the data we have already. >> Pointers? >> >> Cheers, >> >> Markus >> >> >> _________________________________________________ >> Wikidata-l mailing list >> Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.org >> > >> https://lists.wikimedia.org/__mailman/listinfo/wikidata-l >> <https://lists.wikimedia.org/mailman/listinfo/wikidata-l> >> >> >> >> >> >> _______________________________________________ >> Wikidata-l mailing list >> Wikidata-l@lists.wikimedia.org >> https://lists.wikimedia.org/mailman/listinfo/wikidata-l >> >> > > _______________________________________________ > Wikidata-l mailing list > Wikidata-l@lists.wikimedia.org > https://lists.wikimedia.org/mailman/listinfo/wikidata-l >
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