[netmod] ECA model draft: Exception handling

[Qin Wu <[e-mail]>]

*        Not all errors can be detected at configuration time. Error that occur while ECA logic is being evaluated will cause the server to generate an eca-exception notification.
-      Q1:Does an exception cause the ECA entry to be disabled automatically?
-      Q2: What else exceptions and details parameters need to be defined?
*        Proposal to Q1:
-      In case of one time ECA, it will generate exception notification, stop executing other actions associated with the same event, exit ECA execution process
-      In case of periodical ECA execution, it will generate exception notification, stop executing other action associated with the same event, exit ECA execution process in the current period, move to the next period, if the same exception is generated, the ECA entry will be disabled, send another exception notification;

*        Proposal to Q2:

-      The action can be executed in the form of RPC function or function call, therefore function invoke error, rpc invoke error should be defined, in addition, we may allow bind policy variable with xpath expression, variable binding unknown should be defined to cover exception case. When ECA entry can be disabled, the corresponding notification can be generated, we can call it eca entry disable exception.