Re: [netmod] choice/case in tree diagrams

Martin Bjorklund <mbj@tail-f.com> Mon, 05 March 2018 14:27 UTC

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Date: Mon, 05 Mar 2018 15:27:54 +0100 (CET)
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To: j.schoenwaelder@jacobs-university.de
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From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [netmod] choice/case in tree diagrams
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Martin Bjorklund <mbj@tail-f.com> wrote:
> Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> wrote:
> > On Mon, Mar 05, 2018 at 02:54:18PM +0100, Martin Bjorklund wrote:
> > > > 
> > > > So it seems the running code got it right. ;-)
> > > 
> > > As the author of that code, I think that was purely by accident...
> > > 
> > > But I'm not convinced it is the correct solution.  We have one example
> > > in the other thread where someone was confused by the "rw" flag and
> > > thought that it implied that the node would be present in the data
> > > tree.
> > >
> > 
> > So what does rw mean?
> > 
> > (i)  The schema node has a rw property.
> > (ii) The schema node can be instantiated and the instantiated data node
> >      has a rw property.
> > 
> > I think it is difficult to have both at the same time. If the tree is
> > a representation of schema nodes, then (i) seems to make more
> > sense. That said, the explanation in 2.6 is somewhat vague since it
> > says 'data' and not 'nodes' (like everywhere else):
> > 
> > OLD:
> > 
> >        <flags> is one of:
> >          rw  for configuration data
> >          ro  for non-configuration data, output parameters to rpcs
> >              and actions, and notification parameters
> > 
> > NEW:
> > 
> >        <flags> is one of:
> >          rw  for configuration data nodes
> >          ro  for non-configuration data nodes, output parameters to rpcs
> >              and actions, and notification parameters
> 
> I think this is ok.  But that means that we also have to add:
> 
>            --  for a choice or case node
> 
> But in order to be consistent, we should probably have:
> 
>            --  for a choice, case, input or output node

Whoops, it shouldn't be "--".  Somehow we should say that no flags are
used for choice,case,input,output.


/martin


> 
> 
> This means that the correct tree syntax for choice and case will be:
> 
>      +-- (subnet)?
>         +-- :(prefix-length)
>         |  +--rw prefix-length?   uint8
>         +-- :(netmask)
>            +--rw netmask?         yang:dotted-quad
> 
> 
> /martin
> 
> 
> > The document (as far as I searched for it) does not clearly say that
> > 'node' means 'schema node'. In hindsight, it might have been useful to
> > explicitely import terminology from RFC 7950 and to use it carefully
> > (RFC 7950 has 'schema node' and 'data node' but here we largely talk
> > about 'nodes' - and my assumption is that this means 'schema nodes'.)
> 
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