An interface device for connecting at least one process controller to one or more peer devices (3a-3d), comprising: • a process controller interface for bidirectional communication with the process controller; • a peer device interface for bidirectional OPC UA communication with the peer devices (3a-3d); and • a logic unit that is configured to: in response to one or more inputs from the process controller, and/or from the one or more peer devices (3a-3d), meeting one or more predetermined conditions, ∘ determine one or more to-be-performed actions from the one or more inputs according to a predetermined logic; ∘ determine, according to the predetermined logic, one or more outputs which, when supplied to the process controller, and/or to the peer devices (3a-3d), cause the to-be-performed actions to be performed; and ∘ supply these outputs to the process controller, and/or to the one or more peer devices (3a-3d), characterised in that the process controller interface comprises at least one I/O port that is mapped to a variable of the logic unit, and wherein the process controller interface is configured to enable a process controller that has only I/O ports available for inputting and outputting of data and is thus purely data-driven, and not aware of OPC UA in any way, to communicate with the OPC UA peer device (3a-3d) by: • upon a write request to the I/O port by the process controller, reading an input written to the I/O port by the process controller, and updating the value of the variable according to this input; and • upon a read request to the I/O port by the process controller, and/or upon an update to the variable by the logic unit, supplying the value of the variable to the process controller by means of the I/O port, wherein the predetermined logic specifically comprises: • determining, from the input written to the I/O port by the process controller, a call to at least one OPC UA method (3a1-3a3) of a peer device (3a-3d) as a to-be-performed action; and/or • determining, from the read request to the I/O port by the process controller, a call to at least one OPC UA method (3a1-3a3) of a peer device (3a-3d) that causes an update of the variable as a to-be-performed action. • a process controller interface for bidirectional communication with the process controller; • a peer device interface for bidirectional OPC UA communication with the peer devices (3a-3d); and • a logic unit that is configured to: in response to one or more inputs from the process controller, and/or from the one or more peer devices (3a-3d), meeting one or more predetermined conditions, ∘ determine one or more to-be-performed actions from the one or more inputs according to a predetermined logic; ∘ determine, according to the predetermined logic, one or more outputs which, when supplied to the process controller, and/or to the peer devices (3a-3d), cause the to-be-performed actions to be performed; and ∘ supply these outputs to the process controller, and/or to the one or more peer devices (3a-3d), characterised in that the process controller interface comprises at least one I/O port that is mapped to a variable of the logic unit, and wherein the process controller interface is configured to enable a process controller that has only I/O ports available for inputting and outputting of data and is thus purely data-driven, and not aware of OPC UA in any way, to communicate with the OPC UA peer device (3a-3d) by: ∘ determine one or more to-be-performed actions from the one or more inputs according to a predetermined logic; ∘ determine, according to the predetermined logic, one or more outputs which, when supplied to the process controller, and/or to the peer devices (3a-3d), cause the to-be-performed actions to be performed; and ∘ supply these outputs to the process controller, and/or to the one or more peer devices (3a-3d), • upon a write request to the I/O port by the process controller, reading an input written to the I/O port by the process controller, and updating the value of the variable according to this input; and • upon a read request to the I/O port by the process controller, and/or upon an update to the variable by the logic unit, supplying the value of the variable to the process controller by means of the I/O port, • determining, from the input written to the I/O port by the process controller, a call to at least one OPC UA method (3a1-3a3) of a peer device (3a-3d) as a to-be-performed action; and/or • determining, from the read request to the I/O port by the process controller, a call to at least one OPC UA method (3a1-3a3) of a peer device (3a-3d) that causes an update of the variable as a to-be-performed action.