Re: [yang-doctors] Yangdoctors last call review of draft-ietf-ospf-yang-09

[Juergen Schoenwaelder <[e-mail]>]

On Mon, Jan 15, 2018 at 10:38:19AM +0100, Ladislav Lhotka wrote:
> > 
> > The intention (for better or worse) was that the value would use the
> > prefix used in imports.  This means that if you want to do any kind of
> > comparision of the string value to some known identities, then you
> > must import that module so that there is a prefix defined.  This was
> 
> This is IMO not true. As I already wrote, for using a when expression like
> 
>    when "../type = 'ospf:ospfv3'"
> 
> it is not necessary to import the "ietf-ospf" module and thus have the "ospf"
> prefix defined. If you think it is necessary, then point me to the relevant
> text.

Prefixes assigned to modules using the prefix statement are not
guaranteed to be globally unique. It is possible to have multiple
modules defining the prefix 'ospf', e.g.:

 module ietf-ospf {
   prefix ospf;
 }

 module acme-ospf {
   prefix ospf;
 }

Note that this is not a problem since YANG allows to redefine the
prefix in an import statement in case a prefix clash occurs. Hence,
the 'ospf' prefix in the when statement has to refer to the prefix
that is used in the module where the when statement is defined. And
because of that it is necessary to import a module that defines the
prefix 'ospf'. Any other interpretation would be ambiguous I think.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
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