Wikidata:Property proposal/property scope

property scope

Originally proposed at Wikidata:Property proposal/Generic

Done: property scope (P5314) (Talk and documentation)

Description	constraint system qualifier to define the scope of a property
Represents	property scope constraint (Q53869507)
Data type	Item
Domain	Wikidata property (Q18616576) (in the constraints section as a qualifier to property constraint (P2302) → property scope constraint (Q53869507) claims)
Allowed values	as main value (Q54828448), as qualifier (Q54828449), as reference (Q54828450)
Example	VIAF ID (P214) → property constraint (P2302) → property scope constraint (Q53869507) with qualifiers "property scope" → as main value (Q54828448) and "property scope" → as reference (Q54828450)
Planned use	streamline property constraints system; see also: Wikidata talk:WikiProject property constraints#Change of format for scope constraints

Motivation

To restrict the use of properties to certain scopes, we use constraint types used for values only constraint (Q21528958), used as qualifier constraint (Q21510863), and used as reference constraint (Q21528959) for quite a while now. These values are to be used directly as main values for the property constraint (P2302) property on property pages. However, they have some inherent exclusiveness which makes it difficult to permit 2-out-of-3 scenarios (such as main value + qualifier, but not reference). This model has been defined in November 2015.

Recently, another model emerged which tries to address the described issues of the old model. A new property constraint property scope constraint (Q53869507) was proposed by Ivan A. Krestinin, in which the permitted uses should be added as qualifiers with the hereby proposed property "property scope" (see example in the box above). The intended behavior is:

No property constraint (P2302): property scope constraint (Q53869507) → property scope undefined; property may be used everywhere
property constraint (P2302): property scope constraint (Q53869507) without any "property scope" qualifiers → invalid situation; property may be used everywhere
property constraint (P2302): property scope constraint (Q53869507) with one or two "property scope" qualifiers → formally correct, use of property allowed as indicated by the properties (standard use case for the proposed property)
property constraint (P2302): property scope constraint (Q53869507) with all three possible "property scope" qualifiers → formally correct, but equivalent to no use of this constraint type; property may be used everywhere

It is worth to mention here that there has been work and dispute in this story, mainly regarding procedural issues regarding this switch—not regarding our opinion about the old and new model. Full story at Wikidata talk:WikiProject property constraints#Change of format for scope constraints. WMDE has expressed some sympathy for the new approach (see that topic as well), but right now both, the old and the new model, are in use in properties. Unfortunately, for the new model some constraint-related items had been repurposed in the meantime, so that there was some confusion how to excape from this unpleasant situation. It is generally accepted among the participants of the linked discussion that either the old or the new model should be marked deprecated once there is a clear comparison possible. The deprecated model will be faded out then, with enough time for tool devs to adapt the better model. However, to evaluate the advantages of both models, they need to be set up in parallel for a while.

@Ivan A. Krestinin,