1. A virtual assistant system to control external services via messaging, the virtual assistant system comprising: a mobile device configured to participate in a messaging session between a plurality of other participants, to receive an input command from a user, to translate the received input command into a semantic atom, and to transmit the semantic atom via an actionable message to the messaging session, the messaging session supporting a plurality of messaging functions including receiving, transmitting, and displaying messages targeted to one or more of the plurality of participants; and an assistant server configured to receive the semantic atom via the actionable message, the assistant server including at least one plugin, the plugin corresponding to a respective external service and configured to generate a proprietary language command corresponding to the received semantic atom, the proprietary language command controlling the corresponding external service to perform an external function corresponding to the input command; wherein the external function performed by each external service comprises a function other than the messaging functions supported by the messaging session.