1. A system comprising: an input device configured for receiving user dialogue input; an output device configured to output system dialogue output; processing circuitry; an interface communicative coupling the processing circuitry to a plurality of service provider components; and a data storage device that stores definitions of a plurality of atomic dialogue activities, a plurality of complex dialogue activities, a plurality of atomic service processes, and a plurality of complex service processes; wherein: each of the complex dialogue activities is formed by an ordered subset of the plurality of atomic dialogue activities; each of the complex service processes is formed by an ordered subset of the atomic service activities; the processing circuitry is configured to: responsive to a first user dialogue input obtained via the input device, select one of the complex dialogue activities and one of the complex service activities; execute the selected complex dialogue activity by executing at least some of the atomic dialogue activities of the selected complex dialogue activity; insert a node that corresponds to the selected complex dialogue activity in a hierarchical dialogue structure that hierarchically records nodes that correspond to the atomic dialogue activities of one or more of the complex dialogue activities, and that represent respective user dialogue inputs and system dialogue outputs; execute the selected complex service activity by executing the atomic service activities of the selected complex service activity, the execution of the atomic service activities including obtaining a service by one or more of the plurality of service provider components via the interface; responsive to a second user dialogue input, use the hierarchical dialogue structure to determine whether the second user dialogue input corresponds to any of the nodes of the hierarchical dialogue structure that have been recorded for the selected complex dialogue activity; and execute an algorithm by which the processing circuitry updates the hierarchical dialogue structure to include a new node representing the second user dialogue input such that the new node is hierarchically associated with other nodes representing the selected complex dialogue activity when the determination is that the second user dialogue input corresponds to at least one of the nodes that have been recorded for the selected complex dialogue activity, and otherwise is set as a new top hierarchical level node corresponding to another of the complex dialogue activities which is responsively invoked; and the execution of at least one of the atomic dialogue activities of the selected complex atomic dialogue activity uses an output of the execution of at least one of the atomic service activities of the selected complex service activity.