A provisioning engine for provisioning communications services and a pattern language for configuring the provisioning engine. A plurality of objects can be assembled to define provisioning models representing state machines for carrying out common provisioning operations. The state machines include a set of plural current states of the provisioning model, mechanisms for generating signals, tasks, and at least one transition operative to define conditions under which the tasks are executed and states are added to or removed from the set of current states. Signals can be executed instantaneously or scheduled for later execution to permit provisioning operations to be controlled in a temporal manner. The provisioning models can be executed as specific instances and instances can include calls to other models to be executed as subinstances.