This is the first implementation of a new feature supporting the storage of configurations applied to resources, as well as a dry-run feature to compare configurations before applying. 

The executor support three operations: fetch, store and diff. 

Resource configuration snapshots can either be of type RUNNING or CANDIDATE, the latter being a new configuration to be applied to a resource.  The diff operation allows to compare RUNNING vs CANDIDATE snapshots, either in xml or json formats. 

The output of these comparison, are  structured either as a json or xml patch (simplified) payload : 

application/json-patch+json [RFC6902]
[   
  {"op":"move","path":"/system-uptime-information/source-of-time","from":"/system-uptime-information/time-source"},    {"op":"move","path":"/system-uptime-information/system-boot-time","from":"/system-uptime-information/system-booted-time"},   
  {"op":"replace","path":"/system-uptime-information/last-configured-time/user","value":"developer"}
]

application/xml-patch+json [RFC5261]
<?xml version="1.0" encoding="UTF-8"?>
<diff>
  <replace sel="/output[1]/interface-information[1]/interface-flapped[1]/@seconds">2343</replace>
  <replace sel="/output[1]/interface-information[1]/interface-flapped[1]/text()[1]">34</replace>
  <replace sel="/output[1]/interface-information[1]/traffic-statistics[1]/input-packets[1]/text()[1]">09098789</replace>
  <replace sel="/output[1]/interface-information[1]/traffic-statistics[1]/output-packets[1]/text()[1]">2828828</replace>
  <add sel="/output[1]/interface-information[1]/physical-interface[1]">
       <interface-name>TEGig400-int01</interface-name>
   </add>
</diff>