Feature/issue 782 simplify units. Fixes #782.

[uscholdm]

Made a bunch of changes to simplify and clean up things as described in #782 . Main changes are:

• UnitOfMeasure is now a subclass of Magnitude
• No more product or ratio or simple units

This is ready for a preliminary review to get early feedback and catch any mistakes.

STILL TO DO:

• release notes
• examples

Details

• StandardUnit

  • Renamed CoherentUnit to StandardUnit (Coherent Unit is an altLabel)
  • Defined StandardUnit to be equivalent to a UnitOfMeasure that
    • has conversion=1
    • has itself as a standard unit
  • Added a scopeNote indicating that this captures the idea of dimension
  • New standard units
    • Add square meter as the standard AreaUnit
    • Add cubic meter as the standard VolumeUnit .

• UnitOfMeasure

  • Defined UnitOfMeasure to be equivalent to a Magnitude that:
    • has numericValue =1 (it's not called 'unit' for nothing)
    • has itself at its unit of measure
    • has conversion=1
    • has a standard unit
  • Removed UnitOfMeasure from disjoints where incorrect or redundant
  • Moved an annotation about units from Magnitude to a better home: UnitOfMeasure
  • Removed and deprecated SimpleUnitOfMeasure
  • Removed redundant typing of BaseUnits, can be inferred from enumeration.
  • Properties
    • Made hasStandardUnit functional
    • Removed and deprecated hasBaseUnit. Use hasStandardUnit instead

• Removed product and ratio units and magnitudes

  • Removed: ProductUnit, CoherentProductUnit, ProductMagnitude
  • Removed: RatioUnit, CoherentRatioUnit, RatioMagnitude
  • Removed uses and mentions of product and ratio unit and magnitude classes and updated definitions and annotations accordingly.
  • Percentage was redefined because it had been a subclass of RatioMagnitude which was defined in terms of RationUnit. The old definitions were inserted as blank nodes to retain same formal meaning.

• Aspect

  • Made Aspect not a subclass of Category. Aspects such as like length, or inner diameter or cycle time do not exist for the purpose of categorizing things.
  • Made Aspect a subclass of SchemaMetaData. An aspect is a representation of a property connecting two things. It has roughly the same meaning as an OWL property.

• Magnitude

  • Fixed erroneous definition of Magnitude
  • Added examples for Magnitude
  • Renamed Extent to Distance for naming consistency.
  • Renamed MolarQuantity to MoleQuantity for naming consistency.
  • Renamed CountingUnit to CountUnit for naming consistency.
  • Added scopeNote to hasPrecision to say the precision of a Magnitude must have the same StandardUnit as the Magnitude.

[rjyounes]

@uscholdm Closing this PR. Keeping the branch to retain the modifications, but it will be addressed in the general units and magnitudes overhaul.