Re: Proposal to do away with netconf attributes in data model payloads

["Randy Presuhn" <randy_presuhn@mindspring.com>]

Hi -

> From: "Glenn Waters" <gww@nortelnetworks.com>
> To: "Randy Presuhn" <randy_presuhn@mindspring.com>; <netconf@ops.ietf.org>
> Sent: Wednesday, March 31, 2004 10:46 AM
> Subject: RE: Proposal to do away with netconf attributes in data model payloads
...
> > We need to be *very* careful here.  If it is possible to construct
> > multiple
> > names for a single object instance, the handling of relationships (and
> > comparing
> > configurations to determine whether they are equivalent) gets ugly fast.
>
> I agree. XML Schema does not have the concept of unique key or such. As part
> of the data modeling discussion we need to discuss how or if we mark
> attributes as keys (and they must be retrievable, unlike SNMP!)
>
> The way XPath is defined there is no requirement to have unique keys. You
> specify one or more attributes to search on and you get back the set of
> matching objects (it's actually a bit more complex than what I just
> described but conceptually what I described is somewhat accurate).
>
> So if we choose XPath then we may have to subset the features we support to
> fit the network management requirements that we have.

I don't think subsetting XPath would be necessary.  We just need to be
sure that there is a way to determine a "canonical" name of an object instance.
There will be a multitude of XPATH expressions that might find that
object instance (perhaps even independent of its name), but, regardless of
how we've found it, we need to be able to determine what its name is.

...
> > and still begs the question about which normalization form is in use.  I
> > think
> > this has to be nailed down at the protocol level.
>
> I don't know what normalization form means in the context of this work. Can
> you explain.
...

See the big NOTE in the XPATH specification section 3.6.
(http://www.w3.org/TR/xpath#strings) for a good explanation.

Randy



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