Proposal for GPN/GPV of transient objects

docs/guide/proposal_transient_obj_gpn_gpv.md

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+# Proposal for GPN and GPV of transient object
+
+## Proposal 1
+
+Expose the transient nature data elements on USP only, thus it will restrict
+these DM object's visibility on ACS.
+
+### Cons
+
+Customer need to switch to USP to access these DM parameters.
+
+### Effort
+
+Low
+
+
+## Proposal 2
+
+Maintain a cache of whole DM (Device.) each time a session is started and for
+GPV and GPN create the response based on the data available in the cache.
+For SPV and Add/Delete object request perform the operation at lower layer first
+and on success from lower layer update the cache for the effected elements.
+Delete the cache to session end.
+
+### Cons
+
+1. Lot of string processing required and hence the solution will be time taking.
+2. Due to the cache mechanism it will increase memory utilization.
+
+### Effort
+
+High
+
+
+## Proposal 3
+
+A json file will be introduced which will contain the DM path of all transient
+natured objects.
+At the time of session start icwmp will perform GPN for all DM objects declared
+in the json file and store the results in cache.
+
+When GPN request will come from ACS, icwmp will first perform the operation at
+lower layer. Upon receiving the response from lower layer if there exist any
+transient DM parameter then it will validate that path against the cache. If
+that instance is not present in the cache then drop that parameter from final
+result.
+If GPN of any sub object of a transient DM object fails at lower layer but the
+path exist in the cache then instead of error icwmp will return an empty GPN
+response to the ACS but if not exist in cache then will return error.
+
+When GPV request will come from ACS, icwmp will first perform the operation at
+lower layer. Upon failure from lower layer icwmp will validate the path in the
+cache. If the parameter exist in the cache it will return GPV response with
+empty value otherwise will return error.
+
+Delete the cache at session end.
+
+### Cons
+
+1. String processing is required here too but will be optimized by caching only
+the transient natured DM parameters. Still it will increase the operation time
+to some extend.
+2. Memory utilization will also increase to some extend.
+3. In some cases it may return empty value for some parameter's GPV request and
+which may not be a correct value for e.g such parameters which can have value in
+ specific range or specific enum types.
+
+### Effort
+
+Medium