Methods, systems, and computer readable storage medium related to operating an intelligent digital assistant are disclosed. A user request is received, the user request including at least a speech input received from the user. The user request is processed to obtain a representation of user intent, where the representation of user intent associates the user request with a task flow operationalizing a requested task, and the task flow is operable to invoke a plurality of services each supporting functions according to a respective plurality of service parameters. Based on the representation of user intent, one or more relevant task parameters are identified from a plurality of task parameters of the task flow. A subset of the plurality of services are selectively invoked during execution of the task flow, where the selectively invoked subset of the plurality of services support functions according to the identified one or more relevant task parameters.