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Scope: Core (OPC-10000-*) All specs

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OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

2.1.5 Broker

Broker intermediary program module that routes NetworkMessages from Publishers to Subscribers Note 1 to entry: Brokers are building blocks of Message Oriented Middleware
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

2.1.22 NetworkMessage

NetworkMessage to the Message Oriented Middleware (transport layer) to deliver DataSetMessages to the Subscribers . Note 2 to entry: The term message is used with various connotations in the messaging world
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.2 General

addition to the ClientServer model, OPC UA also supports information transfer from Publishers to Subscribers using the PubSub model
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.5 Publish-Subscribe

Publishers send messages to a Message Oriented Middleware , without knowledge of what, if any, Subscribers there may be. Similarly, Subscribers express interest in specific types of data, and process messages ... Oriented Middleware is the network infrastructure that is able to route datagram-based messages. Subscribers and Publishers use datagram protocols like UDP multicast. A broker-based form, where the Message
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.6 Synergy of models

Above all, the PubSub Information Model for configuration promotes the configuration of Publishers and Subscribers using the OPC UA ClientServer model. Figure 7 depicts a single OPC UA Application that ... require such a role dependency. I.e., Clients can be Publishers and Servers can be Subscribers . In fact, there is no necessity for Publishers or Subscribers to be either a Server
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.7.1 General

independent interactions between UA Applications (i.e. between Clients and Servers and between Publishers and Subscribers ). However, as the number of Applications in a given system grows, there are advantages
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.7.8 Security Key Service (SKS)

Security Key Service (SKS) OPC UA Publishers and Subscribers utilize a security key service (SKS) to secure the messages sent between them. The SKS is responsible for managing the keys ... centralized where a single SKS is used by a group of Publishers and Subscribers in a system. The SKS is described
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.2.4 Application Crashes

attacker could also be a Publisher that issues a Message that would cause Subscribers to crash
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.5 Message alteration

could be captured or modified and forwarded to OPC UA Client s, Servers, and Subscribers . Message alteration could allow illegitimate access to a system. Message alteration impacts Integrity, Authorization, Auditability
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.6 Message replay

Message s could be captured and resent to OPC UA Client s, Servers and Subscribers at a later stage without modification. An attacker could misinform the user or send
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.7 Malformed Messages

data values, and send them to OPC UA Client s, Servers or Subscribers . The OPC UA Client , Server or Subscriber could incorrectly handle certain malformed Message s by performing unauthorized
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.5.3.2 Broker-less

application Authentication as well as user Authentication . This approach allows all applications ( Publishers and/or Subscribers ) in a SecurityGroup to share information. An SKS could be part of a Publisher ... Publishers in a SecurityGroup and the frequency of messages. To ensure that Publishers and Subscribers can maintain communication, they need to be able to interact with
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.5.3.3 Broker

many cases the Middleware requires the authorization of both the Publishers and the Subscribers before they can interact with the Broker . The Broker interactions can provide security mechanisms to meet
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.6 SecurityPolicies

Publish Subscribe communications pattern, the SecurityPolicy is associated with a published DataSet and all Subscribers utilize the same SecurityPolicy . Since computing power increases every year, specific algorithms that are considered ... Server and Publisher products implement these policies rather than define their own. Clients and Subscribers support the same policies
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.13 OPC UA security related Services

message. It will encrypt the body of the message and sign the entire message. Subscribers will utilize the keys to decrypt and verify the signature of the messages. These keys
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

H.1 Overview

encoders used for Publishers support all four encodings and all decoders for Subscribers support the ReversibleEncoding, CompactEncoding and VerboseEncodings
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

3.1.2 DataSetClass

used to type DataSets for use in several Publishers and for filtering in Subscribers
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

4.1 Fields of application

application In PubSub the participating OPC UA Applications with their roles as Publishers and Subscribers are decoupled. The number of Subscribers receiving data from a Publisher does not influence
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

4.3 Decoupling by use of middleware

assume the roles Publisher and Subscriber . Publishers are the sources of data, while Subscribers consume that data. Communication in PubSub is message-based. Publishers send messages to a Message Oriented ... Middleware , without knowledge of what, if any, Subscribers there may be. Similarly, Subscribers express interest in specific types of data, and process messages that contain this data, without knowledge
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

4.4 Synergy of models

PubSub Information Model for configuration (see 9 ) promotes the configuration of Publishers and Subscribers using the OPC UA Client Server model. Nevertheless, the PubSub communication does not require such ... dependency. I.e., OPC UA Clients can be Publishers and OPC UA Servers can be Subscribers . In fact, there is no necessity for Publishers or Subscribers to be either
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.1 General

entities. It illustrates the flow of messages from a Publisher to one or more Subscribers . The PubSub communication model supports many other scenarios; for example, a Publisher may send ... receive messages from multiple Publishers . Figure 2 - Publisher and Subscriber entities Publishers and Subscribers are loosely coupled. They often will not even know each other. Their primary relation
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.2.3 DataSetMetaData

Name=DeviceName, Type=String [2] Name=Temperature, Type=Float, Unit=Celsius, Range={1,100} Subscribers use the DataSetMetaData for decoding the values of a DataSetMessage to a DataSet . Subscribers ... DataSetMessage also includes the version of the DataSetMetaData that it complies with. This allows Subscribers to verify if they have the corresponding DataSetMetaData . The related ConfigurationVersionDataType is defined
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.3.3 DataSetMessage

configured time period, a keep alive DataSetMessage is sent to signal the Subscribers that the Publisher is still alive. DataSetMessages are either sent cyclicly or acyclicly in a publishing interval
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.3.6 Transport security

ensured with the transport security between Publishers and the Broker as well as Subscribers and the Broker . The Broker level security in addition requires all Publishers and Subscribers to have
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.3.7 SecurityGroup

security settings and security keys for a subset of NetworkMessages exchanged between Publishers and Subscribers . The security keys are used to encrypt and decrypt NetworkMessages and to generate and check ... within the SKS. A Publisher for its PublishedDataSets needs to know the SecurityGroupId . For Subscribers the SecurityGroupId is distributed as metadata together with the DataSetMetaData . The metadata for a SecurityGroupId
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.2.2 Message reception

example, an additional dispatching step may map the received values to Nodes in the Subscribers OPC UA AddressSpace . The configuration for such a dispatching is called SubscribedDataSet . The two concrete ... configuration of TargetVariables allows the dispatching of DataSetMessage fields to existing Variables in the Subscribers OPC UA AddressSpace . The configuration of SubscribedDataSetMirror is used if the received DataSet fields should
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.4 Configuration Tool

information to be included into messages and also the frequency the messages are sent. Subscribers can use discovery mechanisms to find Publishers and to get the DataSetMetaData necessary to understand ... file using the UABinaryFileDataType . Such a configuration can be used to configure Publishers and Subscribers if they do not have a online configuration interface or are configured through product-specific
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.5.1 General

SecurityGroup into a Publisher or Subscriber . The Method is exposed by Publishers or Subscribers that have no OPC UA Client functionality. The Method is part of the PublishSubscribeType defined
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.5.2 SecurityGroup Management

example for setting up a SecurityGroup and the configuration of affected Publishers and Subscribers is shown in Figure 10 . Figure 10 - SecurityGroup management sequence To secure NetworkMessages , the NetworkMessages shall ... Permissions in the SKS. To set the SecurityGroup relation on the Publishers and Subscribers , the SecurityGroupId and the SKS EndpointDescriptions are configured in a PubSub group
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.5.3 Key acquisition handshakes

Figure 11 . The handshake to push the keys from an SKS to Publishers and Subscribers is shown in Figure 12 . Figure 11 - Handshake used to pull keys from ... Figure 12 - Handshake used to push keys to Publishers and Subscribers To push keys, the SKS creates an encrypted connection to a Publisher or Subscriber and provides credentials that allow
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.5.4 Authorization Services and Security Key Service

Permissions assigned to the SecurityGroup Object identified by the GetSecurityKeys Method arguments. Publishers and Subscribers can request keys if the Access Token they provide is mapped to Roles that have
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.6.3.1 General

Broker . Fan out can be handled to a very large list of Subscribers , multiple networks or even chained Brokers or scalable Brokers . Publisher and Subscriber lifetimes do not have
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

5.4.6.3.2 Broker-based model

Message Oriented Middleware will be a Broker that relays NetworkMessages from Publishers to Subscribers . The Broker may also be able to queue messages and send the same message to multiple ... Subscribers . Note that the Broker functionality is outside the scope of this document. In terms of the messaging protocols, the Broker is a messaging server (the OPC UA Publisher
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

6.2.3.7.1 PublishedData

array of PublishedVariableDataType . The index into the array has an important role for Subscribers and for configuration tools. It is used as a handle to reference the Value in DataSetMessages ... received by Subscribers . The index may change after configuration changes. Changes are indicated by the ConfigurationVersion of the DataSet and applications working with the index shall always check the ConfigurationVersion
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

6.2.3.8.2 SelectedFields

index into the list of entries in the SelectedFields has an important role for Subscribers. It is used as handle to reference the Event field in DataSetMessages received by Subscribers
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

6.3.1.3.1 General

DataSetOffset provide information about the static position of the DataSetMessage in a NetworkMessage Subscribers can rely on. If the value of one of the two parameters is 0, the position
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.2 MessageTypes

discovery messages are required to send discovery information from the Publishers to the Subscribers that do not have out of band knowledge about available Publishers . A Message Oriented Middleware where ... known addressing schema for queues or topics to provide discovery messages to Subscribers . Such a Topic tree is defined for the MQTT transport protocol mapping in 7.3.4.7 . The mapping
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.3 SequenceNumber in headers

modulo 4.294.967.296 Lower bound 1.073.741.824 2^30 Upper bound 3.221.225.472 2^32-2^30 Subscribers shall discard the records they keep for sequence numbers if they do not receive messages
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.4.1 General

sizes of DataSetMessages are typically necessary for the processing of messages in generic Subscribers . If such fields are not present, the Subscriber must know the missing information from the DataSetReader
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.4.3 Error handling

information from the Publisher into DataSetMessages , settings to send them in NetworkMessages to the Subscribers and settings to process the DataSetMessages on the Subscriber side. The error handling ... process received messages without further knowledge of the Publisher side configuration. But most Subscribers need at least the DataSetMetaData to be able to process the received DataSetMessages . The Publisher side
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.4.4.2 NetworkMessage layout

until the new key is used. The Publisher needs to give Subscribers a reasonable time to request new keys. The minimum time is five times the KeepAliveTime configured ... PubSub group. This flag is typically set if all keys are invalidated to exclude Subscribers , who no longer have access to the keys. Bit range 4-7: Reserved Reserved bits
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.4.5.5 Data Key Frame DataSetMessage

encoded but the following structure shall not be encoded into the DataSetMessage . Generic Subscribers can detect heartbeat DataSetMessages if the DataSetMessage size equals the header size. If the DataSetMessage size
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.4.6.1 General

General Discovery announcement messages are sent from the Publisher to the Subscribers and they can be sent through any Message Oriented Middleware and protocol mapping. Discovery announcement messages are used ... inform Subscribers about configuration changes in the Publisher . They are sent by the Publisher in the case of a configuration change. A Publisher can also be configured to send
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.2.5.4.2 VerboseEncoding

DataSetMessages . The VerboseEncoding and the following rules for DataSet field encoding ensure that Subscribers without OPC UA knowledge get messages without OPC UA specific information for normal use cases ... rules for special cases and abstract data types ensure that OPC UA aware Subscribers can fully reverse the payload to OPC UA DataTypes if they have access to the DataSetMetaData
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.3.4.1 General

messages between applications that cannot communicate directly. Publishers send MQTT messages to MQTT brokers. Subscribers subscribe to MQTT brokers for messages. A Broker may persist messages so they ... Subscriber is not online. Brokers may also allow messages to be sent to multiple Subscribers . The MQTT protocol defines a binary protocol used to send and receive messages from
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.3.4.4 Connection properties

converted to a String for the ClientID. MQTT version 5.0 allows Publishers and Subscribers to provide MQTT connection properties as part of opening the connection. The connection properties apply
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

7.3.4.7.1 General

provide context and other information about the message. Topics are hierarchical paths that allow Subscribers to use wildcards to select multiple Topics . Therefore, Topics are most useful when they follow ... Prefix> into multiple Topic levels. Note that using multiple Topic levels prevents Subscribers from automatically discovering Publishers in the system unless they are preconfigured with the <Prefix
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

8.1 Overview

network service used to manage keys for all Publishers and Subscribers or it can be part of a Publisher to manage the keys for the NetworkMessages sent by this Publisher
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

8.3.2 GetSecurityKeys Method

valid after a SecurityGroup is removed or keys for a SecurityGroup are revoked. However, Subscribers shall be prepared for Publishers using invalid keys until they have called the GetSecurityKeys Method ... still request more than one key to bridge longer unavailability time of the SKS. Subscribers should use a StartingTokenId of 0 the first time they call GetSecurityKeys . Subsequent call
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

8.3.3 GetSecurityGroup Method

permissions for the keys. The SecurityGroupId is the identifier for the SecurityGroup in Publishers , Subscribers and the key Server . This Method returns the NodeId of the corresponding SecurityGroup Object Node
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

8.4.1 SecurityGroupType definition

historical keys stored by the SKS. The historical keys are necessary to allow Subscribers to request keys for older NetworkMessages
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

9.1.2 Configuration behaviours

Configuration behaviours Publishers and Subscribers may be configurable through vendor-specific engineering tools or with the PubSubConfiguration Object and parameters described in this document. This allows a standard
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

9.1.4.3.1 PublishedDataItemsType

index into the list of entries in the PublishedData has an important role for Subscribers and for configuration tools. It is used as a handle to reference the entry ... configuration actions like RemoveVariables or the Value in DataSetMessages received by Subscribers . The index may change after configuration changes. Changes are indicated by the ConfigurationVersion and applications working with
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

9.1.4.3.2 AddVariables Method

shall be added at the end of the list in PublishedData . This ensures that Subscribers are only affected by the change if they are interested in the added Variables
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

9.1.4.4.1 PublishedEventsType

index into the list of entries in the SelectedFields has an important role for Subscribers. It is used as handle to reference the Event field in DataSetMessages received by Subscribers
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

A.2.1.2 Overview

PublishingInterval Note: These assumptions have to be fulfilled by appropriate configuration of the Publisher . Subscribers have to know the static message layout in advance. This means all fields
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

C.3 Publish-Subscribe

Publishers send messages to a Message Oriented Middleware , without knowledge of what, if any, Subscribers there may be. Similarly, Subscribers express interest in specific types of data, and process messages ... data, without knowledge of what Publishers there are. Figure C.2 illustrates that Publishers and Subscribers only interact with the Message Oriented Middleware which provides the means to forward the data
OPC-10000-14 – OPC Unified Architecture - Part 14: PubSub

C.4 Synergy of models

PubSub Information Model for configuration (see 9 ) promotes the configuration of Publishers and Subscribers using the OPC UA Client Server model. Nevertheless, the PubSub communication does not require such ... other words, OPC UA Clients can be Publishers and OPC UA Servers can be Subscribers . In fact, there is no necessity for Publishers or Subscribers to be either
OPC-10000-17 – OPC Unified Architecture - Part 17: Alias Names

D.1.2 PubSub multicast messages

shall be used by all applications supporting this optional extension. Subscribers will create a subscription to the provided multicast address for the DataSetClassId. Subscribers can filter on the PublisherId
OPC-10000-25 – OPC Unified Architecture - Part 25: Object Serialization

6.3.7 CustomMetaDataProperties Property

CustomMetaDataProperties Property DataSetMetaData describe the content and the semantics of a DataSet . Subscribers use this metadata to interpret the DataSet from the DataSetMessage and can evaluate the Properties field
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

5.1 Overview

concepts for standard communication between Servers and Clients as well as Publishers and Subscribers , but additional concepts are required for OPC UA FX. These concepts include Connection establishment and bidirectional
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

5.5.6.2.5 DataSetMetaData

Publisher and the Subscriber , including how to encode and decode the DataSetMessage . Thus, Subscribers must know about the PublishedDataSet's DataSetMetaData . For the concepts of the DataSetMetaData and its definition
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

6.12.2 ConnectionEndpointParameterType definition

ConnectionManager can obtain any required information related to this preconfigured StandaloneSubscribedDataSet from the UA Subscribers exposed PubSub configuration. The Publisher is required to provide all data in the StandaloneSubscribedDataSet
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

6.13.3.3 SubscriberConfigurationType definition

Subscriber requires additional information from the parent object, which applies to all Subscribers . Table 99 - SubscriberConfigurationType definition Attribute Value BrowseName 4:SubscriberConfigurationType IsAbstract False References Node Class BrowseName DataType TypeDefinition
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

E.1.3.3 Multiple logical connections - multiple AutomationComponents

Figure E.5 , which shares the same set of parameters for the unicast Publishers and Subscribers . Figure E.5 - Multiple logical connections using multicast (variant
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

E.2.2.1 For logical connections between two AutomationComponents

configuration values (e.g., PublisherId , WriterGroupId , and DataSetWriterId ) to match the Publisher and its corresponding Subscribers . However, unique IDs could be generated by the addressed AutomationComponent and are not known
OPC-10000-81 – OPC Unified Architecture - Part 81: UAFX Connecting Devices and Information Model

E.5 Interaction with an SKS

parallel, which could mean that the SKS configuration completes before all of the Subscribers and Publishers are configured (each configuration is processed in a separate thread). Figure E.24 - Updating ... been configured by the ConnectionManager and current keys have been distributed to Publishers and Subscribers . For the push model, the SKS continues to retry pushing keys using SetSecurityKeys