Re: [netconf] YANG attributes in a datastore

Hi,

YANG already has the "annotation" statement to define metadata.
YANG has data-def-stmt to define data.  It would be very unwise
to use metadata inside a leaf as if it were a leaf inside a container.

Andy

On Tue, Dec 10, 2019 at 7:31 AM Ladislav Lhotka <lhotka@nic.cz> wrote:

> On Tue, 2019-12-10 at 14:58 +0000, Balázs Lengyel wrote:
> > Hello,
> > If we try to standardize editing metadata, we will face a number of
> issues
> > that need to be clarified:
> >
> > - Will you model whether the attribute (metadata) is writable?  Config is
> > not an allowed substatement in
> https://tools.ietf.org/html/rfc7952#section-3
>
> In my view annotations should never be configuration because they should
> not
> influence the device state. The read-only/read-write propertly might be
> useful.
>
> > - Can a metadata have other additional properties? (mandatory,
> cardinality,
> > uniqueness of some kind?)
>
> By design, annotations do not have a specific place in the schema, so they
> cannot be mandatory.
>
> Cardinality: if you mean annotations with a list of values, this was
> discussed
> but rejected due to difficulties with XML encoding.
>
> > - If it is modified, will it be subject to validation, error-messages?
> Will
> > a bad metadata result in a failed error-config?
>
> I would say yes because otherwise it makes no sense to define them and
> their
> properties.
>
> Lada
>
> >
> > Regards Balazs
> >
> > -----Original Message-----
> > From: netconf <netconf-bounces@ietf.org> On Behalf Of Martin Bjorklund
> > Sent: 2019. december 10., kedd 15:04
> > To: mvasko@cesnet.cz
> > Cc: netconf@ietf.org
> > Subject: Re: [netconf] YANG attributes in a datastore
> >
> > Hi,
> >
> > Michal Vaško <mvasko@cesnet.cz> wrote:
> > > Hello,
> > > we are thinking about adding support for arbitrary attributes [1] in
> > > our YANG/NETCONF datastore. To my knowledge, only the representation
> > > in XML or JSON is defined and standardized but there are no guidelines
> > > for editing (CRUD) these attributes.
> > >
> > > So, my question is a rather general one, regarding implementations
> > > that support editing these attributes, would you mind sharing some
> > > basic ideas or principles used? Or is this outside any consensus and
> > > each implementation is free to handle this completely in its own
> > > fashion? Thanks for any input.
> >
> > I think this depends on the attribute defintion.  Some attributes are
> > read-only from the northbound's protocol point of view.  Internally in
> the
> > server you may need some API to set/change them of course.  Some other
> > attributes are read-write.
> >
> > In our implementation we support a few read-write attributes (and some
> > read-only).  Here's a simple example (in an edit-config):
> >
> >   <foo annotation="hello"/>
> >
> > This would set/change the "annotation" attribute's value to "hello",
> > regardless of its previous value.
> >
> > To delete an annotation, you would do:
> >
> >   <foo annotation=""/>
> >
> > Each of our attributes has a special value that means "delete" (in most
> > cases it is the empty string.
> >
> >
> > /martin
> >
> >
> >
> >
> > > Regards,
> > > Michal
> > >
> > > [1] https://tools.ietf.org/html/rfc7952
> > >
> > > _______________________________________________
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> > >
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> --
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
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