Re: [YANG] keyref

On Tue, Jan 22, 2008 at 02:50:14PM +0100, Balazs Lengyel wrote:
> In the Ericsson DML we had something like
>
> leaf my-if-status> {
>   type instance-identifier {
>     refers-to /if:interfaces/if:ifEntry/adminStatus;
>   }
> }
>
> and in the XML
>
>   <myIfStatus>/if:interfaces/if:ifEntry["if:ifIndex=2"]/adminStatus</myIfStatus>
>
> This is quite simple, it works as a leafref as well, and works with 
> multiple keys. refers-to restricts the kind of instance identifiers you can 
> actually use. The actual XML value is somewhat more complicated, but I 
> think the instance identifier format is quite intuitive even for people 
> unfamiliar with XPATH.

It is actually unclear to me what the example does. I get back an
xpath expression that points to some other object to consult? I
believe this is not really the same as the current keyref and this
also raises questions related to referential integrity or what if the
expression actually refers to a node set with more than 1 node and
similar things. I am also not sure management applications and humans
like to extrace the ifIndex value 2 out of the expression. And then
there is the question why to ship redundant information at run time if
it is already hard wired in the scheme? What happens if the expression
is not consistent with refers-to?

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>

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