In the interaction model shown in Figure 3, a Controllerrepresents a control automation component typically implemented in a PLC or DCS controller. Today, devices may be connected to Controllersand can be as simple as an inductive proximity switch or as complex as a Coriolis flowmeter or servo drive. In the future, devicesmay communicate directly with Compute, eliminating the overhead of a Controlleracting as an intermediary. Compute's hardware aspect scales from a single-board computer-based data gateway to a blade server in the cloud. Examples of Computeinclude historians, analytics, and complete MESs.

These interactions can be depicted by dividing the participants into different categories: Controller-to-Controller, Controller-to-Device, Controller-to-Compute, Device-to-Device, and Device-to-Compute. The interactions within these categories are similar in many ways, but each category will include interactions unique to its use cases. Controllersand devicesmay have vastly different functions and roles; however, their functionality is modelled at an abstract level in UAFX as an AutomationComponent (see 6.2). While capabilities specific to Compute-to-Computeare not part of UAFX, these interactions will inherit and benefit from the increased harmonisation delivered at the field level.


Figure 3– OPC UA FX Interaction Model