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

On 2020-02-17 20:47, Christian Hopps wrote:
 >
 >
 >> On Feb 17, 2020, at 11:51 AM, Randy Presuhn <randy_presuhn@alumni.stanford.edu> wrote:
 >>
 >> Hi -
 >>
 >> On 2/17/2020 3:15 AM, Christian Hopps wrote:
 >> ...
 >>> BTW, I did look at the "SHOULD be avoided" (occurs twice that I saw) once dealing with LFs and CRs which lucky for us is not part of a tags allowable characters.
 >>
 >> There are lots of other things that complicate life.  The Yang string definition
 >> circumscribes some of them, but not all.
 >>
 >>> "
 >>>       typedef tag {
 >>>         type string {
 >>>           length "1..max";
 >>>           pattern '[\S ]+';
 >>>         }
 >>> "
 >>
 >> This pattern doesn't make sense to me when I try to understand it using
 >> https://www.w3.org/TR/2004/REC-xmlschema-2-20041028/#charcter-classes
 >> It excludes "symbols", but permits, for example, paragraph separators and
 >> formatting characters and such delights as zero-width non-joiner. Also, in
 >> complementing the "all symbols" category, it seems to me it already permits
 >> space, so I don't see why it calls out space again.

\S is not the *complement* of the "all symbols" category, it *is* the
"all symbols" category - a.k.a. the complement of \s ([#x20\t\n\r]).

 > The intent was to have the pattern match the description immediately below it:
 >
 > "A tag value is composed of a standard prefix followed by any type 'string' value that does not include carriage return, newline or tab characters."
 >
 > Does this pattern fail in doing that?

No, as far as I can see that is exactly what it does.

--Per

 > If this requires anymore work to get right then I think we should drop the pattern, as this isn't the document to come up with a better way to deal with the apparent ugliness of UTF strings in 
YANG. The overriding intent is to leave it to the users to decide what they want to put in there.
 >
 > Thanks,
 > Chris.
 >
 >> Randy
 >>
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