IEC 62769-5-2021 pdf free download – Field device integration (FDI) – Part 5: Information Model.
4 Overview of oPc Unified Architecture
4.1General
The main use case for OPC standards is the online data exchange . between devices and HMI,or SCADA systems. In this use case,the device data is provided by an oPC server and isconsumed by an oPC clientintegrated in the HMI or SCADA ‘system. oPC providesfunctionality to browse through a hierarchicalnamespace containing data items and to read,write and monitor these items for data changes. Numeric identifiers for Nodelds are defined in
Annex A.
oPC UA incorporates features like Data Access，Alarms and Historical Data via platformindependent communication mechanisms and’generic,extensibleand object-orientedmodelling capabilities for the information a system wants to expose.
The current version of oPC UA defines an optimized binary TCPprotocol for high-performance intranet communication as well as a mapping to Web Services. The abstractservice model does not depend on a specific protocol mapping and allows adding newprotocols in the future.Features like security,access control and reliability are directly builtinto the transport mechanisms. Based on the platfom independence of the protocols，OPcUA servers and clients can be directly integrated into devices and controllers.
The OPC uA information model provides a standard way for Servers to expose Objects toClients，Objects in OPC UA terms are composed of other Objects，Variables and Methods.OPC UA also allows relationships to other Objects to be expressed.
The set of Objects and related information that an OPC UA Server makes available to Clients
is referred to as its AddressSpace.The elements of the OPC UA Object Model arerepresented in the AddressSpaceas a set of Nodes described by’Attributes andinterconnecled by References. OPc UA defines various classes of Nodes to representAddressSpace components，most importantly Objects，Variables,Methods,ObjectTypes,DataTypes and ReferenceTypes. Each NodeClass has a defined set of Attributes.
Objects are used to represent components like folders，Devices or Networks. An Object isassociated to a corresponding ObjectType that provides definitions for that Object.
Variables are used to represent values.Two categories of Variables are defined: Propertiesand DataVariables.
Properties are Server-defined characteristics of Objects，DataVariables and other Nodes.Properties are not allowed to have Properties defined for them.An example for Properties ofObjects is the Manufacturer Property of a Device.
DataVariables represent the contents of an Object. DataVariables may have componentDataVariables. This is typically used by Servers to expose individual elements of arrays andstructures.This document uses DataVariables mainly to represent the Parameters of Devices.
4.2Overview of OPc UA Devices
The oPC Unified Architecture for Devices (DI)(IEC 62541-100) standard is an extension ofthe overall oPC Unified Architecture”standard series and’ defines information modelsassociated with Devices. IEC 62541-100 describes three models that build upon each otheras follows:
The (base)Device Model is intended to provide a unified view of devices irespective of the underlying device protocols.
The Device Communication Model adds Network and Connection information elements sothat communication topologies can be created.
The Device Integration Host Model finally adds additional elements and rules required for host systems to manage integration for a complete system. It allows reflecting the topology of the automation system with the devices as well as the connecting communication networks.
The Devices information model specifies different ObjectTypes and other AddressSpace elements used to represent Devices and related components such as the communication infrastructure in an OPC UA AddressSpace. The main use cases are Device configuration and diagnostic, but it allows a general and standardized way for any kind of application to access Device-related information.IEC 62769-5 pdf download.