On Thu, Jan 8, 2015 at 12:17 PM, Federico Leva (Nemo) <nemowiki@gmail.com> wrote:

Thad Guidry, 08/01/2015 18:58:

Unless the P17 Country property had an expanded definition of "sovereign
state (or originating sovereign state) of this item"

That's more like P27. Both are rather flexible though, see their talk pages.
https://www.wikidata.org/wiki/Property_talk:P17

1. How does Wikidata want to handle Property / Statement rule
enforcement and Freebase's incompatible types ?

I'm not sure how this is an example of "incompatible" type, it sounds more like a type Freebase didn't have. Handling such differences is possible by tweaking property descriptions and adding constraints. P17 is already declared incompatible with "instance of: human". If you make "music band" a subclass of "human", then this statement about U2 will be reported by bots as a constraint violation.

Right, Freebase would not stick a Property called "Country" right on an instance of a Music Band.  We would put Country under the Musical Group type, and give it a better definition like "The nation or territory that this item originated from".  Freebase's Properties always live under a Freebase Type, like "Musical Group".  Which is why on Wikidata, even seeing P17 on the U2 topic page makes me wonder what kind of schema Wikidata is trying to pull off.  But it appears that someone did not really read the description page of P17, like I just did, then they would see it just is not allowed like that, but instead should have used P27, but then you can't have a date of birth for a Musical Group (band), which voids using even P27 on an instance of band.

I understand, there are many holes in Wikidata's schema currently.  I am one of several Freebase experts coming over that can help Wikidata identify those problematic Schema. :-)

 

2. How does Wikidata want to handle locking down Property descriptions
(Freebase uses Permissions and Owners), where the complete meaning of
something being changed might cause severe wrongful polluted data ?

There is no such thing in wikis.
http://c2.com/cgi/wiki?WikiDesignPrinciples
https://meta.wikimedia.org/wiki/The_wiki_way

But Wikidata is not a "wiki" in the true sense, or should not be purported as one.... Because it is not Schema-less, but in fact, prescribes to a publicly editable and agreed upon Schema model.

One thing I did notice is that the Wikidata Schema model is actually composed of both agreement on the 2 tabs of https://www.wikidata.org/wiki/Property_talk:P17  both the Property tab, AND the Discussions tab....combined...give the effective model of the Property...whereas in Freebase, we would just have the Property, where all rules and definitions about it are stored (Discussions about a Property were stored on our wiki and also our mailing list).  I enjoy the Wikidata way a bit more compared to Freebase, the benefit being a primary place to see the defines of the Property as well as the Discussion and questions about it in the past.

 

The errors are corrected after the fact; the central control system is not made of permissions, but of checks like the constraint violations bots mentioned above. What other pollutions of the data you have in mind?

And that is my worry.  That the Schema model is publicly editable at any time.  And constraint violations are only effective against a "Well Defined Property".  But what if I do not Well Define that property, or worst, I completely change the meaning of that Property.  Imagine if I suddenly change the meaning of one of your MySQL table columns... like, PERSON suddenly becomes FURNITURE.  That can happen with Wikidata's publicly editable Schema model....if someone maliciously changes the description of that P17 Country to something very generic like "a state".... oh really ?  What kind of state ?  Nations only ? Or territories considered as an organized political community under one government.? or both ?  it appears that P17's Discussion clarifies this a bit, and defines it a bit more narrowly and would not allow just any territory with a political community.

We have the same problem in Freebase, where if by public agreement, we change the meaning of a Property so much that it might cause erroneous data statements, then we deprecate that Property and create a new one, splitting off the various statements into their proper form and letting the Community know, and also performing the data tasks to subscribe the old data to the new Schema.

The pollution of data would happen if by agreement P17's Discussion page drastically changed the intended meaning of it, then all the data that used P17 would need to be cleaned up.

How does Wikidata intend to deal with those kinds of changes to Property meanings in the future ? and the data cleanup involved ?