On Thu, Jan 8, 2015 at 12:17 PM, Federico Leva (Nemo)
<nemowiki(a)gmail.com <mailto: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 ?
Given enough
eyeballs, all unconstructive edits are shallow. That's how
wikis work.
In case a property becomes deprecated in favor of a different one, we
use bots <https://www.wikidata.org/wiki/Wikidata:Bots> to migrate
existing data (e.g. this task
<https://www.wikidata.org/wiki/Wikidata:Requests_for_permissions/Bot/SamoaBot_45>).