Re: [netmod] Alexey Melnikov's Discuss on draft-ietf-netmod-module-tags-07: (with DISCUSS)

[Randy Presuhn <[e-mail]>]

Hi -

On 2/17/2020 2:14 PM, Christian Hopps wrote:
...
> If you are talking about the property categories (where I see 'Z' 
> mentioned as "All separators") then there doesn't appear to be a 
> "lower means include, upper means exclude" relationship. Also it 
> appears that to refer to one of these things the syntax is actually 
> "\P{Z}" or "\p{Z}" not just "Z". So translating maybe that's "[\P{Z} 
> ]"? I see nothing that defines how "catEsc" (\p{}) vs "compEsc" (\P{}) 
> are different, but maybe the upper here means exclude.

My error.  You're right that "[\P{Z} ]" is what the grammar would require
to eliminate all the space-like things while still allowing #x20 space.
The problem with "\S" is that the only kind of space it eliminates is #x20,
(which you then add back in in the regular expression) while Unicode has
a whole menagerie of other space-like creatures one might well want to
exclude from tags while still permitting #x20, as well as lots of other 
stuff
that is probably a bad idea to permit in tags.  That said...

> I'm more inclined to just ditch any pattern or restriction the more 
> this gets discussed. Let the user do what they want. If they want to 
> include crazy unicode stuff (almost certainly they dont) then I guess 
> that's what they want.

Yeah, doing so is almost a design pattern in Yang:  try to constrain 
things with
regular expressions, find out the expression is either too limiting or 
allows too
many invalid strings, then give up.  :-)  No judgement here - it is what 
it is, and
"done" has to take precedence over "perfect."

Randy