1. A method for configuring flow control among policy groups used in a network device processing a packet stream, the method comprising: (a) providing a configuration interface, executing on a device, identifying a plurality of policy groups for configuring a network device, each of the plurality of policy groups comprising policies to be processed consecutively; (b) identifying, by the configuration interface, a first policy of a first policy group of the plurality of policy groups; the first policy of a first policy group specifying a rule comprising an object-oriented expression that evaluates a portion of a network packet; (c) receiving, via the configuration interface, information identifying a second policy group of the plurality of policy groups to be processed based on an evaluation of the expression of the rule of the first policy in the first policy group; (d) evaluating the portion of the network packet using the object-oriented expression; and; (e) processing the second policy group based on the evaluation of the expression of the rule of the first policy in the first policy group.