Re: [I18ndir] I18ndir last call review of draft-ietf-regext-dnrd-objects-mapping-06

["Asmus Freytag (c)" <[e-mail]>]

On 3/6/2020 7:45 AM, John C Klensin wrote:
> [2] It might be of interest that there are two reasons we don't
> have "_" in LDH-style domain names because they were prohibited
> in the original host name syntax.  And they were prohibited
> there precisely because of a human factors argument: when
> reading the handwriting of others, people cannot reliably
> distinguish between "-" and "_", so it is best to allow one and
> not the other.  And the hyphen was chosen in part because the
> most common grapheme for the BCD character that evolved into "_"
> in ASCII (and ECBDIC) was a left-pointing arrow, not a
> horizontal bar at the baseline.  So the ARPANET decided to go
> with a single form at the codepoint level while the Unicode
> decision was to allow different forms and canonicalize later.
> Of course, we have a different variation on the Unicode decision
> with "FWS" and "CWFS" constructions in some well-known protocols.

Unicode's "loose matching" rules are designed to help these
identifiers to be embedded as needed in other protocols, where
there are native restrictions. Unicode does provide an exhaustive
list of what those other protocols might be, but it's been clear
that they include, for examples, programming languages.

Bu making sure identifiers stay unique without requiring literal
hyphens, spaces or underlines, this can be accommodated.

I was simply speculating that for any 'new' protocol that
collects data that have a defined format in other protocols,
it may make sense to not force these data to be normalized
or canonicalized different from what the external protocol expects.

If external protocols allow multiple formats, then it may make
sense to pick one canonical form for the 'new' protocol, just
so data in the new protocol are simplified.

It depends a bit on the use case. A protocol that's a transient
container of data transmitted between implementations
of an external protocol is a different matter from a database
that collects information from potentially different sources,
but could be expected to have some internal consistency.

A./

ps: if/when we get around to writing this down, the language
will need to become much more precise than these musings.