Re: [core] date-and-time and "created-on" field in constrained-voucher

On Mon, Jun 27, 2022 at 2:25 PM Michael Richardson <mcr@sandelman.ca> wrote:

>
> Michael Richardson <mcr+ietf@sandelman.ca> wrote:
>     > 2.  The other thing we ran into was that the CBOR implementation I'm
> using, when given a
>     > DateTime object naturally produces a RFC 8949 Section 3.4.2
> compliant "tag 1" marked Epoch-Based
>     > Date/Time.  And demarshalls this.  So I don't really notice.
>
>     > But, draft-ietf-core-yang-cbor doesn't say much about
> "yang:date-and-time".
>     > The only reference seems to be at:
>     >
> https://www.ietf.org/archive/id/draft-ietf-core-yang-cbor-20.html#name-the-container-and-other-nod
>
>     > where date-and-time is shown as part of a container object.
>     > The Content is defined to be string date pattern.
>
>     > Section 6, where I might expect to see info about encoding dates:
>     >
> https://www.ietf.org/archive/id/draft-ietf-core-yang-cbor-20.html#name-representing-yang-data-type
>
>     > is silent about date and time formats.
>     > https://github.com/core-wg/yang-cbor/issues/144
>
> lemikev wrote in the issue:
>
> l> I'm just not sure this issue is in scope for this draft.
>
> l> "draft-ietf-core-yang-cbor" define the encoding of the built-In types
> l> listed in
> l> [https://datatracker.ietf.org/doc/html/rfc7950#section-4.2.4](url), not
> l> every typedef.
>
> l> [RFC 6021] defines date-and-time as a string with a specific pattern,
> this
> l> is the way these data nodes should be encoded.
>
> l> A clean way to support Epoch-Based Date/Time is to update the
> l> ietf-yang-types YANG module to add this option.
>
> l>  typedef date-and-time {
> l>    union {
> l>      type string {
> l>        pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?'
> l>              + '(Z|[\+\-]\d{2}:\d{2})';
> l>      }
> l>      type unit64;
> l> }
> l>
>

This change is not backward-compatible and not allowed per RFC 7950, sec 11.
A new typedef with a different name is needed to allow the uint64 encoding.

Andy

> l> An alternate option is to use a different typedef in new IoT specific
> YANG modules.
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