Hello all
Apache SIS and GeoAPI depend on JSR-363, "Unit of Measurement"
specification. This specification is currently under revision. There is
of course many ways to design a unit API, but I think that the following
are beyond "arbitrary choices", as they impact our capability to do math
in software:
* The meaning of addition of two quantities (a number with a unit)
shall be the same for everyone. The specification should be specific
enough for ensuring that the result of "A + B" is equivalent
(ignoring rounding errors) in all implementations.
* If A = B, then A+C = B+C
* If A = B, then n*A = n*B
* A + B = B + A (addition commutativity).
While above seem obvious, it actually become tricky with temperature (°C
versus Kelvin). There is different ways to resolve the problem, but my
point is that no matter which solution we choose, it shall obey to above
laws. Otherwise I doubt we can do reliable mathematics with that JSR (it
is still okay if we refrain to use any Quantity operations). However
some JSR members are inclined to do nothing and keep above arithmetic
laws broken, for avoiding to change their implementation. I created two
tickets; if anyone on this list think that the above are important,
could you please add a vote on it?
* https://github.com/unitsofmeasurement/unit-api/issues/98
* https://github.com/unitsofmeasurement/unit-api/issues/99
Martin
