It is assumed that basic concepts of OPC UA information modelling and IEC 61131-3 are understood in this specification. This specification will use these concepts to describe the IEC 61131-3 Information Model. For the purposes of this document, the terms and definitions given in OPC 10000-1, OPC 10000-3, OPC 10000-4, OPC 10000-5, OPC 10000-7, OPC 10000-8, OPC 10000-100, IEC 61131-3 as well as the following apply.

To avoid naming conflicts between IEC 61131-3 and OPC UA terms the prefix Ctrl for controller is used together with IEC 61131-3 terms like Ctrl Variable or Ctrl Program.

Note that OPC UA terms and terms defined in this specification are italicized in the specification.