Re: [core] CoRE @ IETF106: Summary and Minutes

[Cullen Jennings <[e-mail]>]

> On Dec 9, 2019, at 3:42 PM, Carsten Bormann <[e-mail]> wrote:
> 
> 
>  Concerns had been raised about opening up the second registry for
>  derived units, making it harder for a SenML application to find out
>  whether a unit encountered was actually of interest to it.
>  Discussion in the first session resulted in the tentative proposal
>  to mark secondary units with an asterisk (as in "*km/h", as opposed
>  to unmarked "m/s").  Further discussion in the second session made
>  clear that while this makes the use of secondary units stand out, it
>  does not really improve the situation of SenML applications that
>  want to quickly discard measurements for units they do not care
>  about, unless they track the contents of the two registries, which
>  would make the asterisks redundant.

I disagree that the asterisk does not improve the situation

>  There also was some feedback
>  the asterisks would make the adoption of the SenML units registry by
>  other SDOs more difficult.  The in-room consensus not to go for the
>  asterisks, but to include more explanatory text about implementation
>  strategies, needs to confirmed on the mailing list.  

I strongly object to this.  RFC 8428 has a strong assertion that the units 

        For a given type of measurement, there will only be one unit
        type defined.  So for length, meters are defined and other
        lengths such as mile, foot, light year are not allowed.  For
        most cases, the SI unit is preferred.
There is running code that is based on that assumption that has been in production for many years. You can’t break that assumption without some backwards compatibility consideration that help theses deployed applications mitigate the breakage this causes.
The ideas that millions of edge aggregation devices, many on far side of slow links, would query the IANA web server to track the units and decide how to process data seems like a very bad design. I would expect the IESG to reject anything that lead to cases like https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse <https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse>