In the interaction model shown in Figure 3, a Controller represents a control automation component typically implemented in a PLC or DCS controller. Today, devices may be connected to Controllers and can be as simple as an inductive proximity switch or as complex as a Coriolis flowmeter or servo drive. In the future, devices may communicate directly with Compute, eliminating the overhead of a Controller acting 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 Compute include 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. Controllers and devices may 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-Compute are 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