Converting "Newton's law of universal gravitation" Theory Model

[balacij]

Related to #2371

While converting the following TheoryModel into "not an OthModel":

Drasil/code/drasil-example/Drasil/GamePhysics/TMods.hs

Lines 45 to 60 in acf6d8d

	newtonLUG :: TheoryModel
	newtonLUG = tmNoRefs (OthModel newtonLUGRC)
	[qw force, qw gravitationalConst, qw mass_1, qw mass_2,
	qw dispNorm, qw dVect, qw distMass] ([] :: [ConceptChunk])
	[] [newtonLUGRel] [] "UniversalGravLaw" newtonLUGNotes
	newtonLUGRC :: RelationConcept
	newtonLUGRC = makeRC "newtonLUGRC"
	(nounPhraseSP "Newton's law of universal gravitation") EmptyS newtonLUGRel
	newtonLUGRel :: Relation
	newtonLUGRel = sy force $=
	sy gravitationalConst * (sy mass_1 * sy mass_2 /
	(sy dispNorm $^ 2)) * sy dVect $=
	sy gravitationalConst * (sy mass_1 * sy mass_2 /
	(sy dispNorm $^ 2)) * (sy distMass / sy dispNorm)

and in the context of #2426 (comment) , it seems inappropriate to naively convert the following TheoryModel into an EquationalModel because it contains 2 expressions for which it can use to calculate the force. However, if I'm not mistaken, if we want an EquationalModel to mean "something is calculated by this 1 formula", then I think we need to create a new kind of ModelKind to accommodate this.

Assuming I'm correct, would we potentially want some sort of "AnyEquationModel" (weird name, but we can probably figure something out that's better) that contains a list of QDefinitions, for which any can be used to calculate the thing in question?

EDIT: Alternatively, we could even just make "EquationalModels" just allow for this list of QDefinitions describe above, and create a smart constructor for all the existing models that currently have just 1 single related QDefinition.

[balacij]

I believe this is also related to discussion on #1601 (which we may want to visit for other things as well related to ModelKinds in general)

[JacquesCarette]

I agree with the reasoning.

We could indeed use an NEList of expressions (for the right hand sides) in EquationalModels to collapse the two together. But, let's not do that now. Using something from a list requires a choice, but in the 1 case, there is none - and from a design perspective, that's quite different.

I'm thinking EquationalRealm. We use Realm in a paper to mean a theory with multiple interfaces. Let's start with that?

[balacij]

That sounds good to me. I'll try to get that going in a new issue/ticket.