Make UnitOfMeasure a subclass of Magnitude. (Formerly: Undesirable redundancy with gist:_millisecond and gist:_one_millisecond and similar.)

[uscholdm]

We now have:

• gist:_one_millisecond a gist:Magnitude
• gist:_millisecond a gist:UnitOfMeasure

Intuitively, they mean exactly the same thing, so it would be nice to only have one URI. With Magnitude and UnitOfMeasure currently disjoint, we are forced to do this. But what if we could view a unit of measure as simply a magnitude whose decimalValue is 1 and whose unit of measure is itself?

If this can be made to work, we can avoid this unseemly redundancy. I'm looking for a way to do this.

[rjyounes]

Not redundant: the magnitude is a shorthand for one _millisecond.

[uscholdm]

Say I have an individual called :_MichaelUschold and then I create a shorthand :_MikeUschold. The relationship between the two IRIs (e.g. shorthand) does not change the fact that two IRIs are referring to the exact same thing in the world. I am using the word 'redundancy' to refer to that situation.

[rjyounes]

That isn't what I meant by shorthand. I meant shorthand for a resource with a UofM of gist:_millisecond, and decimal value of 1.

[uscholdm]

Lets use a simpler example: second. In the world, this refers to an amount of time. There are two ways to represent this one thing in gist:

1. gist:_second as an instance of DurationUnit which is a subclass of UnitOfMeasure
2. gist:_one_second as an instance of gist:Duration where
   gist:_one_second gist:hasBaseUnit gist:_second
   gist:_one_second gist:decimalValue "1"^^xsd:double

This seems redundant to me, why have two different ways to convey the same information? A second is a second is a second which is a gist:Duration which is a gist:Magnitude. There are two things that are special about gist:_one_second.

1. it's decimalValue is 1 (hence the 'unit' in unit of measure)
2. it points to its ontological self (i.e. semantic double) as the base unit

Here is a sketch of an alternative proposal:

1. Define UnitOfMeasure as equivalentClass to a Magnitude with decimalValue=1
2. Define BaseUnit as equivalentClass to a UnitOfMeasure with itself (literally the same IRI) as its base unit. This will use the lonely underutilized hasSelf restriction.

This way there is no need to create a separate instance of Magnitude for unit magnitudes like 'one millisecond' and all base units.

Caveat:

• I'm not sure how this will work for complex ratio and product units

[rjyounes]

OK, now I see. This is very clever.

[rjyounes]

@uscholdm to prepare brief presentation for discussion on January 30.

[rjyounes]

gist Issue Review 2020-01-30

Michael presented his proposal, with mostly positive reception. For next meeting (Feb 20) he will implement it in a git branch and provide RDF samples.

SteveS finds it to be a category error to say a magnitude is also a unit, and runs counter to his intuition.

[rjyounes]

@uscholdm Is this a major or minor change? Can you please label accordingly? Thanks.