Re: NETCONF Instance Identifiers

[Phil Shafer <phil@juniper.net>]

Andy Bierman writes:
>1) There is a 'fixed' root, starting at <rpc>, for methods
>    and data.  There is also a conceptual 'relative' root for data.
>    This is unnamed, and will be called <config> or <data> or <filter>
>    in a NETCONF PDU.  There is no default namespace associated with
>    the root.

<rpc> or <config>?

>    /foo/bar[x="3",y="4"]

Stick w/ xpath syntax and use "and":

   /foo/bar[x=3 and y=4]

>3) Unnamed instances (e.g. maxOccurs="unbounded") are identified
>    by their position (relative to other instances of the same element),
>    using a special INDEX component called 'position'.  Unnamed
>    instances are numbered starting at zero.  Conceptually, all
>    unnamed, single-instance elements can be identified as position="0".
>
>    E.g.: <goo> is a simple type that can occur 0 or more times
>
>    /foo/bar[x="3",y="4"]/baz[name="fred"]/zoo/goo[position="3"]

This makes "position" a magic token.  In XPath, position() is a
function that does approximately the same thing (origin 1).

    goo[position() = 3]

>4) RPC methods are identified by their path from the absolute root,
>    and instance identifiers used within <error-path> elements may identify
>    the entire path to the <rpc> element.
>
>    /rpc/edit-config/error-option
>
>    /rpc/edit-config/config/interfaces/interface[name="eth0"]

I don't follow you here.  Why would an xpath originated at
/rpc/ be valuable?

>5) If namespaces are used then components within the Xpath expression
>    must consist of properly formatted Qualified Names.
>   /nc:rpc/edit-config/config/acme:interfaces/interface[name="eth0"]

Yup, and don't forget the joys of namespaces and attributes.

But I feel like I'm missing something.  Aren't we really needing
something in the schema that defines what elemenents are identifiers,
rather than XPath syntax for it?  My developer/app needs to know
that the "interface" element is identified by the "name" element
and the most convenient place to "know" this is the schema that
defines the "interface" element.

Thanks,
 Phil

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