This specification describes a unified Process Automation Device Information Model (PA-DIM) that enables protocol and vendor independent data exchange. Figure 6 provides an example illustration of a system in which two Devices interact with several applications running in the cloud and accessing generic and product type data. The Information Model of these two devices includes a standardized device model based on PA-DIM. The model also exposes IEC 61987 semantic dictionary IDs. These IDs may be used by OPC UA clients to obtain the definition of vendor specific data the devices may contain.


Figure 6 - Protocol Independent Information Model

PA-DIM makes use of the Dictionary Reference model defined in OPC 10000-19 and defines the proper International Registration Data Identifiers (IRDI) for entries in the IEC 61987 CDD. The OPC Foundation added a new abstract DictionaryEntryType ObjectType to the OPC 10000-5 specification. It also introduced the new IrdiDictionaryEntryType (Subtype of DictionaryEntryType) ObjectType for semantic information and the HasDictionaryEntry Non-Hierarchical ReferenceType to associate the dictionary entry object to any node.

The PA-DIM, illustrated in Figure 7, defines a base device concept and information model, which is intended to be used for Process Automation Devices. This PA-DIM OPC UA Companion Specification defines the OPC UA BrowseNames and corresponding IEC 61987 Semantic CDD Dictionary IDs. For each Node with a dictionary reference to the IEC Common Data Dictionary, the definition of the referenced CDD entry applies. It is expected, that eCl@ss semantic description will follow the IEC 61987 standardization where applicable.


Figure 7 - PA-DIM

The PADIMType has a HasDictionaryEntry reference to an IRDI representing a class identifier within the IEC 61987 CDD (e.g. Coriolis Flowmeter, Pressure Transmitter, etc.).

The DisplayName Attribute for all Objects, Variables, and Methods with a DictionaryReference in this specification shall be according to IEC 61987 CDD PROPERTY attribute “Short name” or to IEC 61987 CDD CLASS attribute “Preferred name”. DisplayNames are used for configuration dialog displays and are defined within the IEC CDD 61987 CDD according NAMUR NE131 / NOA device parameter names.

PA-DIM defines the Interfaces IAdministrationType for administration purposes and ISignalSetType as a container for process variables (see 7.1.2). The PADIMType includes these Interfaces, and additionally it includes the IDeviceHealthType, provided by OPC 10000-100. Furthermore PADIMType provides a reference to an IRDI dictionary entry to reference the device class (e.g. Pressure Transmitter or Coriolis Mass Flowmeter) and SubDevices Object for modular devices.

Instances of PADIMType represent devices in the real-world. There might be other OPC UA companion specifications representing different aspects of the same real-world device, potentially represented in the same OPC UA Server. Therefore, the guidelines defined in the OPC UA for Devices specification (OPC 10000-100 Annex C) should be followed, when an OPC UA server represents several companion specifications for the same real-world device.

A device is required to provide mandatory functionality. Optional functionality is not required, but if it is provided, it shall be supported as defined.

The IEC 61987 CDD is the source for the definition of properties according to IEC 61987 specification, which have an IRDI dictionary entry. These definitions include a version at the end after the “#” (e.g. #001). For easier readability, some IRDI dictionary definitions have been copied and added to this specification. Although highly unlikely, the IRDI definitions in this specification may deviate from IEC definitions as the IEC specification may change. In such cases the IEC 61987 CDD specification has precedence over the definitions in this specification.

The IRDI dictionary entries are referenced from the TypeDefinitions in this specification. When instantiating the TypeDefinitions, the instances shall have the same IRDI dictionary entries as defined for the TypeDefinitions in this specification. If an instance is based on a subtype, it shall have all IRDI dictionary entries of the subtype, and of the supertypes, as defined in this specification. The same applies for InstanceDeclarations. All instances based on InstanceDeclarations shall have the same IRDI dictionary entries as their InstanceDeclaration. If the InstanceDeclaration is overridden, also the InstanceDeclarations of the supertypes shall be provided. Note: As HasDictionaryEntry Reference is a non-hierarchical Reference and the IRDI Objects do not have ModellingRules, the OPC UA Information Model does not force this automatically.

The primary unit according CDD should be used as default unit and may be modified if applicable.