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Re: NETCONF Instance Identifiers
On Mon, Oct 16, 2006 at 09:05:29PM +0200, Martin Bjorklund wrote:
> Ok. So you mean that these two identifiers would be ok?
>
> /interface[name="eth0"] and /interface[2]
>
> One problem with the second alternative is that it's difficult to know
> whether the string will identify the same object over time, since
> interfaces might come and go.
Oh, this is a classic. I concluded several years ago that there is
simply no way to get this naming right (and I am ignoring the fact
that on some systems you can arbitrarily rename interfaces - did you
ever see what xen 3.0 does to your interfaces when it boots?). How you
best refer to an interface is really something you can only answer
when you understand the purpose of the reference. There are valid
reasons to sometimes refer to an interface with a given name, sometime
you like to refer to an interface with a given address, sometimes you
really like to refer to an interface whose alias matches a certain
regex, sometimes you might have a valid reason to refer to the 2nd
interface. The nice thing about netconf is that it does allow some
freedom which is a clear step ahead of what SNMP gave us.
> > I strongly dislike an approach where certain xpath features (like
> > position()) may only be used under some conditions.
>
> Are you suggesting that any XPath construct should be valid in an
> Instance Identifier? Or do you mean that if position() can be used in
> some places in an Instance Identifier, then it should be possible to
> use it anywhere in the Instance Identifier?
The later. The set of valid xpath constructs needs to be defined and
what belongs to this set should be valid everywhere. Back at the time
when we discussed filtering, I suggested an xpath subset to be used.
Some other IETF WG has adopted a similar approach and they even
defined the subset - I would have to dig to find the reference - it is
somewhere in the netconf archive. The XML directorate might also
know...
/js
--
Juergen Schoenwaelder International University Bremen
<http://www.eecs.iu-bremen.de/> P.O. Box 750 561, 28725 Bremen, Germany
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