Wikidata:Property proposal/items for this type

items for this type

Originally proposed at Wikidata:Property proposal/Generic

   Not done

Description	all the instances/subclasses of the subject item should have the object item or an instance/subclass of the object item
Data type	Item
Domain	qualifier of properties for this type (P1963)
Allowed values	all items
Example	Windows software (Q15593630) properties for this type operating system edit items for this type Microsoft Windows 0 references add reference add value
See also	item of property constraint (P2305)

Motivation

It allows to indicate specific items that every instance/subclass of the subject item should have. Malore (talk) 16:22, 28 April 2018 (UTC)

Discussion

•  Oppose There is already Wikidata item of this property (P1629) David (talk) 10:51, 29 April 2018 (UTC)

 Comment @David: They are two different properties:

• Wikidata item of this property (P1629) is a property applied to other properties and represents the item corresponding to the subject property;
• "items for this type" is a qualifier of properties for this type (P1963) and indicate that all instances/subclasses of the subject item, in addition to sharing a particular property (as a result of properties for this type (P1963)), share also a particular value.--Malore (talk) 11:41, 29 April 2018 (UTC)

•  Comment Ah, I see you have proposed this for item-valued properties too. Anyway, I don't think this is the right approach here... ArthurPSmith (talk) 14:18, 7 May 2018 (UTC)

 Comment@ArthurPSmith: I think there are three approaches:

1. introduce "item constraints": same of "property constraints" but for items. The most powerful because it allows to indicate properties, values, properties that shouldn't be used, etc. and it allows to warn if these constraints are not satisfied;
2. this approach: make normal properties to indicate constraints. Less powerful because it doesn't warn if they are not satisfied but easier to implement;
3. divide item statements in "statements for this item" and "statements for this type": the former refer only to the subject item, while the latter are inherited by the instances/subclasses of the item. It's equivalent to something like "members require statement constraint" with item of property constraint (P2305) qualifier.

I chose the second one because it's easier and quicker to implement--Malore (talk) 16:58, 7 May 2018 (UTC)

@Malore: Hmm, your suggestion 1 I think is a good idea, there have been other situations that seemed to require it (many property constraints are really item constraints on instances of, for example, Q5). However, that probably requires some lengthy discussions with the developers of how to implement and I agree is not likely to be available soon. I was actually thinking something along the lines of your option 3 - to add a qualifier to indicate the scope of a given property statement - i.e. applies to self, applies to instances, applies to all subclasses, etc. I don't think that requires any development. ArthurPSmith (talk) 17:30, 7 May 2018 (UTC)

@ArthurPSmith: I totally agree with you. Such a qualifier is better than using properties like this one because it's not redundant. However, I don't know if there are items where a statement is true only for its instances/subclasses and not for the item itself. In such cases, a qualifier is not adequate.--Malore (talk) 23:42, 8 May 2018 (UTC)

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•  Oppose There is no need to have both value and item versions. Peter F. Patel-Schneider (talk) 16:04, 7 May 2018 (UTC)

 Oppose Just use Wikidata item of this property (P1629), as well as we use connecting line (P81) as both statements and qualifiers. --Liuxinyu970226 (talk) 04:22, 8 June 2018 (UTC)

• marking as  Not done, no support − Pintoch (talk) 08:10, 10 June 2018 (UTC)