VOUnits RFC

[Markus Demleitner]

Hi all,

On Thu, Jul 25, 2013 at 05:54:40PM +0100, Norman Gray wrote:
> In particular (despite some comments on the RFC page and off-line)
> we have not extended the syntax of decimal numbers.  In fact, the
> only place where such a number would appear in this specification
> is in the form of a numerical scaling factor before a unit (for
> example '0.1nm', indicating that the Angstrom is the _unit_, as
> opposed to _quantity_): we restrict such scaling factors to round
> powers of ten, and in any case expect these to be rather rare.

For the record: I am still convinced that that is a restriction we
are going to regret -- allowing arbitrary factors is a small price to
pay for not having to touch data that has, say, "Jupiter mass" as
units and while having IVOA-valid unit strings.  It's *much* nicer to
have to commit to a choice for Jupiter mass, say, only in the
metadata rather than to bake that choice into the data itself.

And, with it, you'd even have "0.0254 m" sanctioned as an IVOA-valid
unit.  Now, wouldn't *that* be nice?

And I also still maintain it's be cheap to allow standard
C/pascal/python/whatever float syntax ("1.3e10") -- it's what
everyone will write these days, it doesn't create ambiguities, it's
cheap, and it follows the principle of least surprise.

Cheers,

          Markus