1. A non-transitory machine-readable medium encoded with instructions for execution by a network device, the medium comprising: instructions for establishing an object representative of a received network message having a network message type, comprising: instructions for configuring the object to access individual fields of the received network message based on network message definition data for the network message type, wherein the network message definition data identifies individual fields carried by messages having the network message type; and instructions for evaluating operator-defined rules at run-time in connection with a received network message, comprising: instructions for accessing, via the object representative of the received network message, a field of the received network message in response to evaluating a reference that identifies the object and that is within an operator defined rule.