is `qudt:applicableUnit` inherited along the QuantityKind hierarchy?

[VladimirAlexiev]

If QuantityKind A ahs parent B (A skos:broader B), then does A inherit qudt:applicableUnit from its parent, or should A enumerate and repeat all applicableUnit?

• This suggests the opposite: that applicableUnits are collected from all children and must apply to the parent : https://github.com/qudt/qudt-public-repo/blob/ac7111711c5e2c891726d3fa0aaa8b90747b4888/schema/SCHEMA_QUDT-v2.1.ttl#L2368-L2373
  • https://github.com/qudt/qudt-public-repo/issues/719 shows that skos:broader is used instead of qudt:generalization, but the question still applies
• The longish discussion in https://github.com/qudt/qudt-public-repo/issues/272 seems to suggest that nothing should be inherited or collected. but I cannot say I've understood all of it
  • (It talks about qudt:appropriateUnit, but there's no such prop: there is qudt:applicableUnit and a number of subprops thereof: SCHEMA_QUDT-v2.1.ttl#L1965C1-L1970)
• Can you document in a scopeNote of QuantityKind whether any inheritance (down the hierarchy) or "collection" (up the hierarchy) is intended?

[VladimirAlexiev]

Examination of https://qudt.org/2.1/vocab/quantitykind shows no inheritance in either direction, eg

• quantitykind:AbsoluteActivity skos:broader quantitykind:InverseVolume
• the child AbsoluteActivity has only one applicableUnit: unit:BQ-SEC-PER-M3
• the parent InverseVolume has many, but not that one:

  qudt:applicableUnit unit:PER-CentiM3 ;
  qudt:applicableUnit unit:PER-FT3 ;
  qudt:applicableUnit unit:PER-IN3 ;
  qudt:applicableUnit unit:PER-L ;
  qudt:applicableUnit unit:PER-M3 ;
  qudt:applicableUnit unit:PER-MilliM3 ;
  qudt:applicableUnit unit:PER-YD3 ;

[steveraysteveray]

Hi. We documented our approach here and, as you point out, in Issue #272 . The description illustrates one reason (using the case of AC power) why we don't want to use fully transitive inheritance. Specifically, while reactive power is a specialization of the more general power quantity kind, it is not correct to use the more general units (watts) when describing a value.

You are correct that we had in the past used appropriateUnit, specialization, generalization, all of which have been retired from use in the vocabularies. We should mark them as deprecated in the schema files.

We never did come to complete closure on Issue #272...

[VladimirAlexiev]

Thanks @steveraysteveray, that's a great answer.

More considerations:

• Please add "See https://github.com/qudt/qudt-public-repo/wiki/Advanced-User-Guide#4-computing-applicable-units-for-a-quantitykind on how qudt:applicableUnit is computed from qudt:hasQuantityKind and then materialized" to the documentation of qudt:applicableUnit
• Please add "qudt:isQuantityKindOf is a strict inverse of qudt:hasQuantityKind. However, it does not express all possible allowed pairs of qudt:Unit and qudt:QuantityKind. See qudt:applicableUnit for a property that expresses all such pairs" to the documentation of qudt:isQuantityKindOf.
• generalization/specialization are not used anywhere, so I think it's better to delete them. If you decide to deprecate instead, please delete the misleading sentences 1,2 from its description

[steveraysteveray]

Good suggestions. Assuming our Board is on board (heh heh), I'll make the changes. (Except I'll just deprecate the generalization/specialization just in case someone out there is using them. We're trying to never delete unless absolutely necessary).

[steveraysteveray]

Resolved in #721