Re: [core] RSSI in SenML

[Christian Amsüss <[e-mail]>]

On Wed, Mar 22, 2017 at 10:54:58PM +0100, Carsten Bormann wrote:
> > By the name, but not by the use. The review guide after the table (esp.
> > point 2) indicate that what is called unit in the document is what SI
> > calls quantities, and the presence of Hz, 1/s and Bq shows that as well.
> 
> Hz, 1/s, Bq are units.
> 
> Quantities that can be expressed in these units are [...]

Yes, they are units (I was inexact here where I shouldn't have been),
but by they are also (in SI terminology) units that have a name, and
with that indicate a (ISO) kind of quantity, sometimes even given
explicitly in the table. It seems to me that ISO calls "unit" what SI
calls "unit with special names", in that ISO unit definition contains
the kind of quantity, but I might be interpreting too much into that the
SI brochure 8 sec. 2.2.2.

> The principles are in ISO80000-1.  (Most of us got our degrees before
> 2009; I just wish students today would work more with these
> fundamentals…)

Thanks for the pointer; this is much more explicit than the SI brochure
that was my main reference on this topic so far.

> > Maybe that should be clarified in the registry introduction; straw man
> > text: "The definitions given here are called units based on common
> > language use. In the terminology of the International System of Units,
> > they are special unit names, and not only indicate the unit but also the
> > described quantity.”
> 
> That would most definitely not be true with most entries of the current table.
> Almost all are units in the SI or ISQ.
> (Yes, there are some entries that are more on the quantity side of the spectrum.)

I still think that the text should be more explicit in that a SenML
registered unit implies a kind of quantity (probably all of them, not
only the second half; maybe make it into a dedicated column?), but can't
really come up with something certainly-correct-yet-concise, and with
the ISO definitions in background, that's less important given their
definition implies a kind for every unit.

Best regards
Christian

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