SubclassOf axiom needed if EquivalentTo axioms exist?

[l-emele]

In the fuel hierarchy we use a lot of equivalent classes. When we create (or converting an existing class to) an equivalent class we usually have both EquivalentTo axioms and SubclassOf axioms. Here are some examples:

Class: 'combustion fuel'
    EquivalentTo: fuel and ('has disposition' some 'combustible energy carrier disposition')
    SubclassOf: fuel

Class: 'liquid fossil fuel'
    EquivalentTo: 'fossil combustion fuel' and ('has normal state of matter' value liquid)
    SubclassOf: 'fossil combustion fuel'

To me, this seems a bit redundant to have express things in both EquivalentTo axioms and SubclassOf. Also this structure has led to at least one error while changing classes (see PR #965).

@OpenEnergyPlatform/oeo-general-expert-formal-ontology : Is it necessary to have in these cases both the EquivalentTo axioms and the SubclassOf axioms? If they are not necessary, would you suggest to delete these SubclassOf axioms?

cc @stap-m

[akleinau]

class fuel as subclass of itself seems a bit redundant.
Apart from that I think that without the SubClassOf axioms protege would need reasoning to find out where the classes belong in the class hierarchy. As the reasoner is mostly deactivated they would just float around somewhere unordered. Which would make working with them complicated.
On the other hand "fuel" has to be included in the equivalentTo statement to avoid things that are not fuel getting classified as such.

[l-emele]

Thanks @akleinau for this answer and welcome back. I did not knew, that you are still watching the OEO project.

class fuel as subclass of itself seems a bit redundant.

Sorry, I copied fuel wrongly resp. mixed there something up. As my question is more specifically on the subclasses of fuel and not fuel itself, I deleted fuel itself from the examples above. Fuel looks correctly like this:

Class: fuel
    EquivalentTo: ('has role' some 'fuel role') and ('has disposition' some 'energy carrier disposition')
    SubclassOf: 'portion of matter'

Apart from that I think that without the SubClassOf axioms protege would need reasoning to find out where the classes belong in the class hierarchy. As the reasoner is mostly deactivated they would just float around somewhere unordered. Which would make working with them complicated.

I did a test: If I delete the axiom SubclassOf: fuel from the class combustion fuel, Protégé still sorts it (with a disabled reasoner) correctly below fuel. I assume that this is because the first part (fuel) of the axiom EquivalentTo fuel and ('has disposition' some 'combustible energy carrier disposition') is not composite in contrast to the second part (('has disposition' some 'combustible energy carrier disposition'))? But maybe I am wrong...

[jannahastings]

@l-emele I think that's right, if the first part of the equivalent classes axiom is a simple superclass then Protege is clever enough to figure out that this must be the superclass and display it accordingly. I'm not sure if all visualisers/editors will be able to do this, but since we only use Protege it should be okay?

[l-emele]

For documentation: We touched this topic in issue #1191 and decided that at least for the moment all equivalent classes should have a simple SubclassOf axiom. Else equivalent classes are shown completely detached from the other classes. We might change this in future, but that is th current state.