Process Automation
Device Information
Model
Technical White Paper

Process Automation Device Information Model

Executive Summary
Today’s process automation field devices communicate with host systems over either analog 4-20mA
connections, sometimes with embedded digital HART data; or via 2-wire digital fieldbus connections conforming
generally to the FOUNDATION Fieldbus (FF) or PROFIBUS PA standards as well as wireless protocols like
Wireless HART or ISA 100.
Initiatives all over the world such as Industrie 4.0 (I 4.0), Industrial Internet of Things (IIoT), Open ProcessAutomation Forum (OPAF) and the NAMUR Open Architecture (NOA) are working on concepts for digitaltransformation.
The enormous installed base in the process industries requires a digital transformation solution which can makeuse of information from devices communicating via current field communication solutions. Each of these existing
communication protocols employs different software structures, or information model, to represent the same
information.
To ensure interoperability and seamless access to device information it is necessary to standardize on the formand basic contents of the information models for certain device classes independent of a specific communication
protocol. Thus enabling seamless instrumentation information flow throughout the enterprise.
FieldComm Group (FCG), OPC Foundation (OPCF) and PROFIBUS/PROFINET International (PI) have taken
the initiative to jointly standardize and specify the information model for Process Automation Devices - PA-DIM.
The work is being performed in the working group structure of FCG with dedicated representatives from OPCFand PI.

– PAGE 1 –Process Automation Device Information Model

Table of Contents
Executive Summary .......................................................................................................................... 1
Technology Trends and Developments .......................................................................................... 3
Unified Information Model - Protocol Agnostic Approach ............................................................ 4PA-DIM and Industrie 4.0.................................................................................................................. 6
Stepwise Approach........................................................................................................................... 6
Installed Base .................................................................................................................................... 7
Semantic Identifiers .......................................................................................................................... 9Outlook ............................................................................................................................................ 10Abbreviations .................................................................................................................................. 11
References ...................................................................................................................................... 11– PAGE 2 –Process Automation Device Information Model

Technology Trends and Developments
Today’s process automation field devices communicate with host systems over either analog 4-20mA
connections, sometimes with embedded digital HART data; or via 2-wire digital fieldbus connections conforming
generally to the FOUNDATION Fieldbus (FF) or PROFIBUS PA standards as well as wireless protocols like
Wireless HART or ISA 100.
Active development is now underway in the IEEE 802.3 committee to create a 2-wire Ethernet standard. Whencomplete, this standard will allow for high-speed (10 Mbit/s) communications for process automation devices.
This standard is known as APL or Advanced Physical Layer. Current projections expect availability of process
automation devices supporting APL around 2020.
APL will allow the implementation of Ethernet based field communication protocols (e.g. PROFINET, HART IP)
at the device level. It will also allow the implementation of OPCUA and the OPCUA information models directly atthe device level, which would lead to simplified system architectures and allowing for seamless communicationfrom device to cloud without the need for specific protocol gateways.
Initiatives all over the world such as Industrie 4.0 (I 4.0), Industrial Internet of Things (IIoT), Open Process
Automation Forum (OPAF) and the NAMUR Open Architecture (NOA) are working on concepts for digitaltransformation and new automation system architectures. Information models are key in all of these approaches
to make device information available to any kind of application in a well-structured and transparent way (figure1). To ensure interoperability and seamless access to device information it is necessary to standardize on theform and basic contents of the information models for certain device classes independent of a specificcommunication protocol.
The enormous installed base in the process industries requires a solution which can make use of informationfrom devices communicating via current field communication solutions such as HART, FF, and PROFIBUS PA.
Each of these existing communication protocols employs different software structures to represent the same
information. Information models shall be applied to provide seamless and interoperable access for software
applications and other devices.

– PAGE 3 –Process Automation Device Information ModelFigure 1: Convergence towards IP-connectivity & semantic integration in plant-wide communication

Unified Information Model - Protocol Agnostic Approach
FieldComm Group (FCG), OPC Foundation (OPCF) and PROFIBUS/PROFINET International (PI) have taken
the initiative to jointly standardize and specify the information model for Process Automation Devices - PA-DIM.
The work is being performed in the working group structure of FCG with dedicated representatives from OPCF
and PNOPI.
PA-DIM is based on the NAMUR requirements for Open Architecture (under development), Self-Monitoring andDiagnosis of Field Devices (NE107) [1] and NAMUR standard device - Field devices for standard applications(NE 131) [2]. PA-DIM covers use cases such as:Provide/receive information to/from HMIs, information apps, reporting apps, etc.

Provide information for inventory management and remote monitoring applications

Provide information that is used by real time control applications

Device configuration and parameterization

Provide interfaces for configuring the security of a device, and for monitoring its current hardeningstatus



Provide information for device dashboardsThe protocol agnostic unified information model will allow software applications to access device information
without additional mapping or protocol specific knowledge. They just need to follow the standardized PA-DIM.
The assignment of Semantic Identifiers according to the Common Data Dictionary (IEC 81987) will enablesoftware applications to “understand” the meaning of PA-DIM contents.
The implementation will be done using OPCUA (IEC 62541 [3]) and the OPCUA for devices (DI, IEC 62541-100[4]) standards. PA-DIM focuses on standardizing a set of information and behavior for specific classes of process
automation devices as defined in [2] NE 131: NAMUR standard device - Field devices for standard applications
independent of a certain communication protocol.

– PAGE 4 –Process Automation Device Information Model

PA-DIM could be implemented directly on native OPCUA devices. This is expected to be the future approach,assuming process automation devices will support communication via Ethernet and the advanced physical layer,
which will enable 2-wire Ethernet, power over the Ethernet wires and installation in hazardous areas.
For current devices the FDI technology [6] provides the means to set up PA-DIM as part of the FDI Information
Model server through the respective device description (EDD). Fieldbus specific information will be mapped tothe defined standard information model (PA-DIM) by the FDI server (Figure 2).

Figure 2: PA-DIM as part of an FDI Server or on a native OPCUA device– PAGE 5 –Process Automation Device Information Model

PA-DIM and Industrie 4.0
Another important input for PA-DIM is the idea of the Asset Administration Shell (AAS) as defined by the I4.0
consortium. Asset Administration Shell and Administration Shell are used synonymously.
The Asset Administration Shell is the standardized digital representation of the asset, cornerstone of theinteroperability between the applications managing the manufacturing systems. It identifies itself and the assets
represented by it, holds digital models of various aspects (sub models) and describes technical functionality
exposed by the Administration shell or respective assets [5].
Sub models are used to structure the information and technical functionality of an Administration shell into
distinguishable parts. Each sub model refers to a well-defined domain or subject matter. Sub models canbecome standardized and thus become sub models types [5].
PA-DIM shall fulfil the requirements for an AAS, it shall standardize sub models of the Administration Shell(Figure 3).

Figure 3: Asset Administration Shell for Process Automation Devices

Stepwise Approach
The PA-DIM shall be developed in a stepwise approach and allow for backward compatible extensions of theinformation model with further sub-models over time.
The first step of the PA-DIM specification (Figure 4) will be based on OPCUA DI (IEC 62541-100 [4]) and be
published as an OPCUA companion specification. It will standardize certain sub-models for the typical processautomation devices (flow, pressure, temperature, level, and positioner):Device Identification (OPCUA DI (IEC 61541) [4], IEC CDD (IEC 61987) [8])Device diagnosis (according to NE 107 [1] ,NE 131 [2])Basic Configuration through Standard Device Parameters (core parameters according to NE 131 [2]Process Variables, NE 131 [2]– PAGE 6 –Process Automation Device Information ModelFigure 4: PA-DIM step 1Future steps may include additional sub-models on comprehensive device configuration and parameterization,security mechanisms, or provide information for an HMI.

Installed Base
For the installed base of process automation devices the PA-DIM is supported by the FDI technology [6]. The
FDI architecture foresees an OPCUA information model represented through an OPCUA server. The structure of
the FDI Information Model is being created from the EDD which is part of the FDI Package and describes all
device related information, business logic and user interfaces.
The overall information model for process automation devices (Figure 5) consists of:Standardized contents specified in PA-DIM
o Device Identificationo Device Diagnostics
o Process Variableso Core Parameters

Generic information as specified in the FDI standard
o User interactiono Business rules– PAGE 7 –Process Automation Device Information Model

By using the FDI information model server, existing plants can be enhanced to expose information from HART,
FOUNDATION Fieldbus or fieldbus devices through OPCUA and the standardized PA-DIM to any kind ofOPCUA client. Information from existing field devices will be mapped to the PA-DIM by FDI mechanisms.

Figure 5: FDI technology enables access to PA-DIM for the installed base– PAGE 8 –Process Automation Device Information ModelSemantic Identifiers
PA-DIM specifies semantic information as required by the NAMUR Open Architecture and I4.0 AAS [5]. The
upcoming editions of OPCUA specification, Part 5 - Information Model (IEC62541-5 [3]), FDI (FCG TS 62679 [6])and EDDL (FCG TS 61804 [7]) enable the assignment of Semantic Identifiers. PA-DIM assigns SemanticIdentifiers as specified in IEC 61987 Common Data Dictionary [8]. By this PA-DIM provides device information ina standardized, machine-readable format.
OPCUA provides the basic infrastructure to reference from an OPC UA Information Model to external data
dictionaries like IEC Common Data Dictionary or eCl@ss. It defines ObjectTypes and ReferenceTypes andexplains how they should be used [3].
The ObjectTypes are used to represent an external data dictionary in an OPC UA Address Space. The
ReferenceType is used to reference from Nodes in the Address Space to the dictionary entries. Such dictionary
entries can be seen as external classification or external semantic [3].
The types and instances defined in OPCUA part 5 are illustrated in Figure 6. The IEC61987DictionaryEntryType
is an example which illustrates how a concrete subtype can be defined to reference dictionary entries in aconcrete external data dictionary [3].

Figure 6: Semantic information dictionary reference types– PAGE 9 –Process Automation Device Information ModelOutlook
PA-DIM will be extended with new sub models, standardizing e.g. security aspects or user interface information
for comprehensive device configuration.
There are trends to implement the OPCUA information model server on field device level. In this case the PADIM will be also embedded on native OPCUA devices. The mapping of protocol specific formats on the FDI
server level will not be required anymore, information from individual native OPCUA devices can be accessed by
OPCUA clients directly or indirectly through aggregated OPCUA servers (Figure 7).
For an OPCUA client there will no difference whether it accesses information from existing field devices mapped
through an FDI server or if it accesses information directly from a native OPCUA field device. The PA-DIM
structure will be the same.

Figure 7: PA-DIM embedded in native OPCUA devices– PAGE 10 –Process Automation Device Information ModelAbbreviations
For the purposes of this document, the following abbreviations apply.
CDD

Common Data Dictionary

EDD

Electronic Device Description

EDDL

Electronic Device Description Language

FCG

FieldComm Group

FDI

Field Device Integration

IMInformation ModelIMS

Information Model Server

OPCUA

OPC Unified Architecture

PA-DIM

Process Automation Device Information ModelPI

PROFIBUS & PROFINET International

UID

User Interface Description

UIP

User Interface Plugin

References[1] NE 107: Self-Monitoring and Diagnosis of Field Devices, NAMUR, 2017[2] NE 131: NAMUR standard device - Field devices for standard applications, NAMUR, 2016[3] IEC 62541: OPC Unified Architecture[4] IEC 62541-100: OPC Unified Architecture for Devices (DI)[5] Platform Industrie 4.0: Details of the Administration Shell, Platform Industrie 4.0, 2018
[6] IEC 62679: Field Device Integration[7] IEC 61804: Electronic Device Description Language (EDDL)[8] IEC 61987: Common Data Dictionary

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Document Number: FCG AG10098, 1.0February 2019©2019 FieldComm Group– PAGE 11 –