merge/replace selection criteria

[Paul Sangree <psangree@cisco.com>]

I believe the current criteria for selecting the target element for a merge 
or replace operation is ambiguous and therefore flawed.  The problem is a 
bit difficult to describe so I'll start with an example.  Suppose the 
current running configuration for a user list, expressed in XML, contains 
two users, John and Bill:

<config>
  <users>
      <user>
         <name>John Smith</name>
         <address>123 A Street</address>
      </user>
      <user>
         <name>Bill Baker</name>
         <address>456 B Street</address>
      </user>
   </users>
</config>

Now suppose John rents out his spare room to Bill, so we need to update 
Bill's address.  We could replace Bill's user entry using the 'replace' 
operator:

<rpc message-id="12345" xmlns="http://ietf.org/xmlconf/1.0/base";>
<edit-config>
   <target>
      <running/>
   </target>
   <config xmlns="http://example.com/schema/userconf"; 
xmlns:xc="http://ietf.org/xmlconf/1.0/base";>
      <users>
         <user xc:operation="replace">
            <name>Bill Baker</name>
            <address>123 A Street</address>
         </user>
      </users>
   </config>
</edit-config>

However, how does the target system know whether we are trying to change 
Bill's address to "123 A Street" or change John's name to "Bill 
Baker"?  Both interpretations are valid but only one yields the desired result.

The problem is that the current netconf syntax does not provide a way to 
explicitly specify which sub-elements are selection keys and which are just 
replacement data.  The same problem holds true for merge operations as well 
(just substitute "merge" for  "replace" in the above example).  Note that 
there is no ambiguity in 'delete' operations, since no replacement data is 
included in the command.


Paul Sangree
Software Developer
Cisco Systems



 

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