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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

2.1.1 AddressSpace

AddressSpace collection of information that a Server makes visible to its Clients Note 1 to entry: See OPC 10000-3 for a description of the contents and structure
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

2.1.4 Attribute

entry: All Attributes are defined by OPC UA, and may not be defined by Clients or Servers . Attributes are the only elements in the AddressSpace permitted to have data values
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

2.1.6 Certificate

identity Note 1 to entry: Certificates are used to identity for example Clients , Servers , users, and certificate authorities
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

3.2 Specification parts

Part 12 specifies how Discovery Servers operate in different scenarios and describes how UA Clients and Servers should interact with them. It also defines Information Models for Certificate management
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.2 General

types, along with flexible object models, to facilitate interoperability and dynamic information discovery by Clients . Supporting a variety of communication protocols and data encodings, such as TCP, HTTPS, WebSockets, XML/text ... both current and historical data, as well as Alarms and Events to notify Clients of important changes. In addition to the ClientServer model, OPC UA also supports information transfer from
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.3 Design goals

Services also include an integrated security model. OPC UA also allows Servers to provide Clients with type definitions for the Objects accessed from the AddressSpace . This allows Information Models ... data may be defined by OPC, other standard organizations or vendors. Through the AddressSpace , Clients can query the Server for the metadata that describes the format for the data
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.4.1.1 General

General OPC UA security is concerned with the authentication of Clients and Servers , the authentication of users, the integrity and confidentiality of their communications, and the verifiability of claims
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.4.1.3 Auditing

provides the capability for Servers to generate Event Notifications that report auditable Events to Clients capable of processing and logging them. OPC UA defines security audit parameters that ... defines the data types for these parameters. Not all Servers and Clients provide all of the auditing features. Profiles, found in OPC 10000-7 , indicate which features are supported
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.4.2 Integrated AddressSpace model

model The set of Objects and related information that the Server makes available to Clients is referred to as its AddressSpace . The OPC UA AddressSpace represents its contents ... inherits these Attributes and may additionally define its own Attributes . To promote interoperability of Clients and Servers , the OPC UA AddressSpace is structured hierarchically with the top levels the same
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.4.4 Integrated services

Integrated services The interface between Clients and Servers is defined as a set of Services. These Services are organized into logical groupings called Service Sets . Service Sets are discussed ... specified in OPC 10000-4 . OPC UA Services provide two capabilities to Clients . They allow Clients to issue requests to Servers and receive responses from them. They also allow Clients
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

4.5 Sessions

points for operations that span multiple requests. Sessions are defined as logical connections between Clients and Servers . Servers may limit the number of concurrent Sessions based on resource availability, licensing
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.1 ClientServer overview

ClientServer overview The OPC UA systems architecture models Clients and Servers as interacting partners. Each system may contain multiple Clients and Servers . Each Client may interact concurrently with ... more Servers , and each Server may interact concurrently with one or more Clients . This model enables Clients to access data, invoke Services , and receive Events from Servers . An application
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.3 Server application

Server . It uses the Server API to send and receive OPC UA Messages from Clients . Note that the " Server API" is an internal interface that isolates the Server
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.4.1 AddressSpace Nodes

AddressSpace Nodes The AddressSpace is modelled as a set of Node s accessible by Clients using OPC UA Services (interfaces and methods). Node s in the AddressSpace are used
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.4.3 AddressSpace Views

Node s or References in the AddressSpace . Views are visible via the AddressSpace and Clients are able to browse Views to determine their structure. Views are often hierarchies, which ... easier for Clients to navigate and represent in a tree
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.5.2 Subscriptions

Subscriptions A Subscription is an endpoint in the Server that publishes Notifications to Clients . Clients control the rate at which publishing occurs by sending Publish Messages
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.6.3 Subscription Services

through the OPC UA Service Interface for the purpose of periodically sending Notifications to Clients . Notifications include Events , Alarms , data changes and Program outputs
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.3.7 Server to Server interactions

provide: aggregation of data from lower-layer Servers , higher-layer data constructs to Clients , and concentrator interfaces to Clients for single points of access to multiple underlying Servers . Figure
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.6 Synergy of models

data stream for continuous monitoring. OPC PubSub can easily be integrated into Servers and Clients . Quite typically, a Publisher will be a Server (the owner of information) and a Subscriber ... PubSub models Nevertheless, the PubSub communication does not require such a role dependency. I.e., Clients can be Publishers and Servers can be Subscribers . In fact, there is no necessity
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

5.7.1 General

mostly concerned with the standardization of the independent interactions between UA Applications (i.e. between Clients and Servers and between Publishers and Subscribers ). However, as the number of Applications ... system. For example, if a system consists of one Server and one or more Clients , it is reasonable for the Server to be configured with the usernames and passwords
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.1 General

Service Sets . Each Service Se t defines a collection of related Services that enable Clients to access specific aspects of a Server's functionality. The Service Sets and their Services ... These Service Set s are fundamental to the ClientServer interaction model, providing Clients with the means to discover Servers , establish secure communication, access and manipulate data, subscribe to events
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.2 Discovery Service Set

Servers that are available in a system. It also provides a manner in which clients can read the security configuration required for connection to the Server . The Discovery Services ... dedicated Discovery Servers . Well known dedicated Discovery Servers provide a way for Clients to discover all registered Servers . OPC 10000-12 describes how to use the Discovery Services with dedicated
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.6 View Service Set

also define Services to create Client defined Views . The View Service Set allows Clients to discover Node s in a View by browsing. Browsing allows Clients to navigate ... References between Node s contained in the View . In this manner, browsing also allows Clients to discover the structure of the View
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.7 Attribute Service Set

Nodes that are defined by OPC UA. They may not be defined by Clients or Servers . Attributes are the only elements in the AddressSpace permitted to have data values
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.8 Method Service Set

always a component of an Object . Discovery is provided through the browse Services . Clients discover the Methods supported by a Server by browsing for the owning Objects that identify their
OPC-10000-1 – OPC Unified Architecture - Part 1: Overview and Concepts

6.10 Subscription Service Set

redundant Client , to receive NotificationMessages from it. To protect against non-use by Clients , Subscriptions have a configured lifetime that Clients periodically renew. If any Client fails to renew ... detection and recovery of lost Messages . Each NotificationMessage contains a sequence number that allows Clients to detect missed Messages . When there are no Notifications to send within the keep-alive
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.2.2 Authentication

Authentication Entities such as Clients , Servers , and users should prove their identities. Authentication can be based on something the entity is, has, or knows
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.2.3 Resource Exhaustion

resource resulting in a single Client obtaining all resources blocking valid Clients from accessing the Server . For example, on a Server in which only 10 Sessions are available a malicious
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.3.12 Rogue Local Discover Server

builds a malicious Local Discover Server . The malicious Local Discover Server could direct Clients to incorrect Servers , lower the exposed security of listed Servers or hide legitimate Servers . It could
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.6 SecurityPolicies

pattern, each Client can select a policy independent of the policy selected by other Clients . For the Publish Subscribe communications pattern, the SecurityPolicy is associated with a published DataSet ... vendors' products, 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

4.12 Roles

approach assigns Permissions to Roles illustrated in Figure 6 . Clients are then granted Roles based on connection information ( Session creation). Roles could be restricted by User Authentication , Application Authentication , SecurityModes
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

4.13 OPC UA security related Services

both the Server and Client derive the SymmetricKeys needed for the secure conversation . Since Clients and Servers have the same set of cryptographic keys they can communicate securely with each
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

5.1.2.2 Message flooding

message size limit, automatically closing connections where the limit is exceeded. The Clients also ignore extra responses that could be received and closes the connection. In PubSub , the Subscriber filters
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

5.1.4 Message spoofing

number, which further restricts Message spoofing. In session-less communication, to counter message spoofing Clients and Server should restrict session-less communication to be over SecureChannel
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

5.1.8 Server profiling

this threat. OPC UA limits the amount of information that Servers provide to Clients that have not yet been identified. This information is the response to the GetEndpoints service specified
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

5.1.12 Compromising user credentials

minimized by restricting Server access in additional manners, such as from specific applications ( Clients ) or at specific times
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

6.7 Administrative access

administrator account access. Administrative AccessRestrictions include items such as configuration files for Servers and Clients . For example, configuration files could contain paths to certificate stores or exposed endpoints both
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

6.11 Audit event management

SecureChannel to ensure they are not tampered with while in transition, for Clients that log audit events; it is recommended that the logged audit events be persisted in such
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

6.19 Diagnostic related issues

overall structure of Server . This type of diagnostic shall only be provided to Authenticated Clients
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

7.1 Overview

point of view. These services, also known as Discovery Services, provide capabilities that allow Clients to discover Servers and connect to them. The Discovery Services are available as local services
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

7.3 Multicast Discovery

security is enabled and all applications use certificate TrustLists to control access. Also, Clients should cache connection information, minimizing the lookup of Server information. However, even
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

8.1 Overview

multiple methods of accessing a GDS: Servers can register with the Discovery Server Clients can query the GDS for available Servers Clients can pull certificates from the CertificateManager Servers ... system. Threats against the GDS, including the presence of rogue Clients or Servers. Threats against the certificate management functionality provided
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

8.2 Rogue GDS

list provided by the Discovery Server and the Server match. This ensures that Clients can determine if the Discovery Server provided valid information. Clients should be aware of rogue Discovery ... Servers that could direct them to rogue Servers . Clients can use the TLS server certificate (if available) to verify that the Discovery Server is a Server that they trust and/or
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

8.4 Certificate management threats

functionality to users with SecurityAdmin Role or comparable access rights. Furthermore, the list of Clients that are allowed to access management functionality can be limited. Certificate management includes a provisioning ... phase. The provisioning phase is when the GDS is providing initial certificate(s) to Clients or Servers that are just entering the system. The runtime phase
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

9.1 Overview

signing a certificate is specified as part of the Security Policy . Servers and Clients should be able to support more than one certificate since more than one certificate could
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

9.2 Self signed certificate management

Client applications that communicate with them. As the number of Servers and Clients grows, the administration effort can become too burdensome. In addition, a Certificate has a lifetime and will ... Public Keys to be copied again. In very small installations, explicitly listing what Clients a Server trusts by installing the Public Key of the Client ApplicationInstanceCertificate in the Trusted Certificate
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

9.3 CA Signed Certificate management

Signed Certificate management In systems with multiple Servers and Clients the installation of Public Keys in TrustLists can very quickly become cumbersome. In these instances, the use of a company ... Figure 12 - CA Certificate handling The administrator generates a CA signed ApplicationInstanceCertificate for all Clients and Servers that are installed in a system, but the administrator will only install
OPC-10000-2 – OPC Unified Architecture - Part 2: Security Model

9.4.1 Overview

GlobalDiscoveryServer with Certificate Management could be deployed. The GlobalDiscoverServer will either push certificates to Clients and Servers or allow Servers and Clients to pull certificates. The GlobalDiscoveryServer certificate management
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.3 Object Model

AddressSpace is to provide a standard way for Servers to represent Objects to Clients . The OPC UA Object Model has been designed to meet this objective. It defines Objects
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.4.1 General

Objects and related information that the OPC UA Server makes available to Clients is referred to as its AddressSpace . The model for Objects is defined by the OPC UA Object
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.4.2 NodeClasses

NodeClasses . No other NodeClasses shall be used to define Nodes , and as a result, Clients and Servers are not allowed to define NodeClasses or extend the definitions of these NodeClasses
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.4.3 Attributes

Attributes Attributes are data elements that describe Nodes . Clients can access Attribute values using Read, Write, Query, and Subscription/MonitoredItem Services . These Services are defined in OPC 10000-4 . Attributes ... indicator. The set of Attributes defined for each NodeClass shall not be extended by Clients or Servers . When a Node is instantiated in the AddressSpace , the values of the NodeClass
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.6.1 General

some cases, the NodeId used by the HasTypeDefinition Reference will be well-known to Clients and Servers . Organizations may define TypeDefinitionNodes that are well-known in the industry. Well-known ... NodeIds of TypeDefinitionNodes provide for commonality across OPC UA Servers and allow Clients to interpret the TypeDefinitionNode without having to read it from the Server . Therefore, Servers may use well
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.6.3 Subtyping

subtyping rules are defined in Clause 6 . Subtyping of ObjectTypes and VariableTypes allows: Clients that only know the supertype to handle an instance of the subtype as if it were
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.7.1 General

EventNotifier Attribute of those Nodes identifies if the Node allows subscribing to Events . Clients subscribe to such Nodes to receive Notifications of Event occurrences. Event Subscriptions use the Monitoring
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.7.2 EventTypes

cannot be returned in an Event Subscription . EventTypes exist in the AddressSpace to allow Clients to discover the EventType . This information is used by a client when establishing and working
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.7.3 Event Categorization

would be established. Refer to the description of the Event ReferenceTypes for additional examples. Clients can select a category or categories of Events by defining content filters that include terms
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.8 Methods

behaviour. Methods are invoked by using the Call Service defined in OPC 10000-4 . Clients discover the Methods supported by a Server by browsing for the owning Objects References that
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.9.1 Overview

ervers should define a base set of Roles and allow configuration Clients to add system specific Roles . Adding, deleting, and modifying Roles is restricted to callers with appropriate permissions. When ... connect to the Server . Endpoint identity can be used to restrict access to Clients running on particular networks. Endpoint identity mappings should not be used as the only criteria unless
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.10.2 Interface Model

applied to an ObjectType another one to the instance Figure 11 - Example: Interface Hierarchy Clients can detect the implementation of Interfaces by filtering for the HasInterface Reference into the Browse ... elements derived from an Interface together with elements of the Node's base type. Clients can also use the TranslateBrowsePathsToNodeId Service with BrowseNames of Interface members to get the NodeId
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

4.10.3 AddIn model

shown in Figure 13 . Figure 13 - Example of AddIn applied to an instance Clients can detect the implementation of AddIns by passing the HasAddIn Reference as filter to the Browse ... Service request. If an AddIn has a default BrowseName, Clients can use the TranslateBrowsePathsToNodeId Service with the default BrowseName to get the NodeId of an AddIn . In the example
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.2.4 BrowseName

string-part of the BrowseName is case sensitive. That is, Clients shall consider them case sensitive. Servers are allowed to handle BrowseNames passed in Service requests as case insensitive. Examples
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.2.5 DisplayName

DisplayName The DisplayName Attribute contains the localised name of the Node . Clients should use this Attribute if they want to display the name of the Node to the user. They ... this purpose. The Server may maintain one or more localised representations for each DisplayName . Clients negotiate the locale to be returned when they open a session with the Server . Refer
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.2.8 UserWriteMask

writeable in the general case that applies for every user. Clients cannot assume an Attribute can be written based on the UserWriteMask Attribute .It is possible that the Server
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.2.10 UserRolePermissions

value of the Attribute is an array of RolePermissionType Structures (see Table 8 ). Clients may determine their effective Permissions by performing a logical OR of Permissions for each Role
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.3.1 General

also define ReferenceTypes . In addition, OPC 10000-4 defines NodeManagement Services that allow Clients to add ReferenceTypes to the AddressSpace . Table 9 - ReferenceType NodeClass Name Use Data Type Description Attributes ... Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.4 View NodeClass

View NodeClass Underlying systems are often large and Clients often have an interest in only a specific subset of the data. They do not need, or want, to be burdened ... thus as the only entry point into a subset of the AddressSpace . Therefore, Clients shall not ignore View Nodes when exposing the AddressSpace . Simple Clients that do not deal with
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.5.1 Object NodeClass

Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure ... Icon O Image The Icon Property provides an image that can be used by Clients when displaying the Node . It is expected that the Icon Property contains a relatively small
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.5.2 ObjectType NodeClass

Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure ... Icon O Image The Icon Property provides an image that can be used by Clients when displaying the Node . It is expected that the Icon Property contains a relatively small
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.5.4 Client-side creation of Objects of an ObjectType

based on an ObjectType , i.e. they have a HasTypeDefinition Reference pointing to its ObjectType . Clients can create Objects using the AddNodes Service defined in OPC 10000-4 . The Service requires
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.6.2 Variable NodeClass

DataType , ValueRank and ArrayDimensions Attributes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure of a Node ... Property provides the localized text representation of the value. It can be used by Clients only interested in displaying the text to subscribe to the Property instead of the value
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.6.5 VariableType NodeClass

DataType , ValueRank and ArrayDimensions Attributes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure of a Node
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.6.6 Client-side creation of Variables of an VariableType

based on a VariableType , i.e. they have a HasTypeDefinition Reference pointing to its VariableType . Clients can create Variables using the AddNodes Service defined in OPC 10000-4 . The Service requires
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.7.1 Method NodeClass

Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure ... shall be set to FALSE if the Executable Attribute is set to FALSE. Clients cannot assume a Method can be executed based on the UserExecutable Attribute . It is possible that
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.8.1 DataType Model

cases, the NodeId of the DataType Node - the DataTypeId - will be well-known to Clients and Servers . Clause 8 defines DataTypes and OPC 10000-6 defines their DataTypeIds . In addition ... industry. Well-known DataTypeIds provide for commonality across OPC UA Servers and allow Clients to interpret values without having to read the type description from the Server . Therefore, Servers
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.8.2 Encoding Rules for different kinds of DataTypes

Built-in DataTypes regarding the encoding they cannot have encodings defined in the AddressSpace . Clients can read the DataType Attribute of a Variable or VariableType to identify the Simple DataType ... encoding of the Structured DataType is transmitted with each value, thus Clients are aware of the DataType without reading the DataType Attribute . The encoding has to be transmitted
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.8.3 DataType NodeClass

Property belongs to. Attribute value changes do not cause the NodeVersion to change. Clients may read the NodeVersion Property or subscribe to it to determine when the structure ... Node has changed. Clients shall not use the content for programmatic purposes except for equality comparisons. EnumStrings O LocalizedText[] Enumeration DataTypes shall have either an EnumStrings Property or an EnumValues
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

5.8.4 DataTypeEncoding and Encoding Information

content of this Attribute shall not be changed once it had been provided to Clients since Clients might persistently cache this information. If the encoding of a DataType needs ... provided, meaning that a new NodeId shall be used for the DataType . Since Clients identify the DataType via the DataTypeEncodings , also the NodeIds for the DataTypeEncodings of the DataType shall
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

6.4.1 Overview

subtype of it. Instances may reference several Nodes with the same BrowsePath . Clients that need to distinguish between the Nodes based on the InstanceDeclarationHierarchy and the Nodes that
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

6.4.4.4.3 ExposesItsArray

Variable representing a specific entry in the array (e.g. the second). Clients will typically either get the array or access the Variables directly, so there is no need to provide
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

7.27 IsDisabledOptionalField

supertype, to indicate that the field shall not be provided. This indicates to Clients , that the Server will never provide the optional field and that they are not allowed
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

8.2.2 NamespaceIndex

underlying system to use the same identifier to identify the same Object . This enables Clients that connect to those Servers to recognise Objects that they have in common. Namespace URIs
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

8.2.3 IdType

system, or across systems (e.g. GUIDs). System-wide and globally-unique identifiers allow Clients to track Nodes , such as work orders, as they move between OPC UA Servers as they ... might or might not be human interpretable. String identifiers are case sensitive. That is, Clients shall consider them case sensitive. Servers are allowed to provide alternative NodeIds
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

8.4 LocaleId

This format is defined in 8.5 . Table 26 shows examples of OPC UA LocaleIds . Clients and Servers always provide LocaleIds that explicitly identify the language and the country/region. Table
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

8.37 UtcTime

Coordinated Universal Time (UTC) values. All time values conveyed between OPC UA Servers and Clients are UTC values. Clients shall provide any conversions between UTC and local time. It should
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

9.5 AuditEventType

Server 's responsibility to provide the Event to any interested Clients . Clients are free to subscribe to Events from the Server and will receive the AuditEvents in response to normal ... optionally persist the AuditEvents in addition to the mandatory Event Subscription delivery to Clients . Figure 44 - Audit Behaviour of a Server Figure 45 illustrates the expected behaviour of an aggregating
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

A.1 Overview

model of the underlying system as well as the requirements of the Clients accessing the OPC UA Server . It is also expected that companion specifications will be developed
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

A.3 ObjectTypes

should be used when some common structures/groups of Objects and/or Variables should be described. Clients can use this knowledge to program against the ObjectType structure and use the TranslateBrowsePathsToNodeIds Service
OPC-10000-3 – OPC Unified Architecture - Part 3: Address Space Model

A.5 Views

used to present an excerpt of the AddressSpace suitable for a special class of Clients , for example maintenance Clients , engineering Clients , etc. The View only provides the information needed
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

1 Scope

Calls (RPC) that are implemented by OPC UA Servers and called by OPC UA Clients . All interactions between OPC UA Clients and Servers occur via these Services . The defined Services
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

3.1.3 DiscoveryEndpoint

DiscoveryEndpoint Endpoint that allows Clients access to Discovery Services without security Note 1 to entry: A DiscoveryEndpoint allows access to Discovery Services without a Session and without message security
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

3.1.4 Endpoint

Endpoint physical address available on a network that allows Clients to access one or more Services provided by a Server Note 1 to entry: Each Server may have multiple Endpoints
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

3.1.10 Redundancy

component Note 1 to entry: This may apply to Server s, Clients or networks
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

4.1 Service Set model

Service Set The View Service Set , illustrated in Figure 5 , defines Services that allow Clients to browse through the AddressSpace or subsets of the AddressSpace called Views . The Query Service ... allows Clients to get a subset of data from the AddressSpace or the View . Figure 5 - View Service Set The Attribute Service Set is illustrated in Figure 6 . It defines
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.3 Service results

administrators and apply to all connections between a Client and a Server . Clients that receive Bad _ EncodingLimitsExceeded faults from the Server will likely need to reformulate their requests. The administrator
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.5.1 Overview

Discovery Services with dedicated Discovery Servers. Every Server shall have a DiscoveryEndpoint that Clients can access without establishing a Session . This Endpoint may or may not be the same Session ... Endpoint that Clients use to establish a SecureChannel . Clients read the security information necessary to establish a SecureChannel by calling the GetEndpoints Service on the DiscoveryEndpoint . In addition, Servers
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.5.3.1 Description

cache it shall assign a monotonically increasing identifier to the record. This allows Clients to request records in batches by specifying the identifier for the last record received
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.5.4.1 Description

this situation, the Server shall return separate EndpointDescription records for each available configuration. Clients should treat each of these configurations as distinct Endpoints even if the physical URL happens ... extremely small. If the message security is NONE then it is possible for Clients to deliberately or accidentally hijack Sessions created by other Clients . A Server may have multiple HostNames
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.5.5.1 Description

Server . This Service will be called by a Server or a separate configuration utility. Clients will not use this Service . A Server shall establish a SecureChannel with the Discovery Server ... only provides its serverUri and the URLs of the DiscoveryEndpoints to the Discovery Server . Clients shall use the GetEndpoints Service to fetch the most up to date configuration information directly
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.5.6.1 Description

FindServersOnNetwork . This Service will be called by a Server or a separate configuration utility. Clients will not use this Service . Servers that support RegisterServer2 shall try to register with
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.6.2.1 Description

expired. To prevent valid Messages from being discarded, the applications should do the following: Clients should request a new SecurityToken after 75 % of its lifetime has elapsed. This should ensure ... that Clients will receive the new SecurityToken before the old one actually expires. Servers shall use the existing SecurityToken to secure outgoing Messages until the SecurityToken expires or the Server
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.7.2.1 Description

handling of these parameters. The Server returns its EndpointDescriptions in the response. Clients use this information to determine whether the list of EndpointDescriptions returned from the DiscoveryEndpoint matches the Endpoints ... provided. A Server application should limit the number of Sessions . To protect against misbehaving Clients and denial of service attacks, the Server shall close the oldest Session that
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.7.2.2 Parameters

rules in 6.1.3 even if the Server chooses to allow connections from untrusted Clients . This validation may have occurred when the SecureChannel was established and does not need
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.7.3.1 Description

increased with repeated failures. Sporadic failures shall not delay connections with valid tokens. Clients can change the identity of a user associated with a Session by calling the ActivateSession Service
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.7.4.1 Description

that are currently outstanding to provide for the timely return of the CloseSession response. Clients are urged to wait for all outstanding requests to complete before submitting the CloseSession request
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.9.1 Overview

Overview Clients use the browse Services of the View Service Set to navigate through the AddressSpace or through a View which is a subset of the AddressSpace . A View
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.9.3.2 Parameters

point in the result set from which the browse response is to continue. Clients may mix continuation points from different Browse or BrowseNext responses. The ContinuationPoint type is described
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.9.5.1 Description

establish a connection to these systems. The RegisterNodes Service can be used by Clients to register the Nodes that they know they will access repeatedly (e.g. Write, Call). It allows ... anything needed so that the access operations will be more efficient. Clients can expect performance improvements when using registered NodeIds , but the optimization measures are vendor-specific. For Variable Nodes
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.11.2.1 Description

constructed Attribute values whose elements are indexed, such as an array, this Service allows Clients to read the entire set of indexed values as a composite, to read individual elements
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.11.3.1 Description

constructed Attribute values whose elements are indexed, such as an array, this Service allows Clients to read the entire set of indexed values as a composite, to read individual elements ... read ranges of elements of the composite. Servers may make historical values available to Clients using this Service , although the historical values themselves are not visible in the AddressSpace
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.11.4.1 Description

constructed Attribute values whose elements are indexed, such as an array, this Service allows Clients to write the entire set of indexed values as a composite, to write individual elements
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.12.1 Overview

component of an Object . Discovery is provided through the Browse and Query Services . Clients discover the Methods supported by a Server by browsing for the owning Objects References that identify
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.1.1 Overview

Overview Clients define MonitoredItems to subscribe to data and Events . Each MonitoredItem identifies the item to be monitored and the Subscription to use to send Notifications . The item
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.1.2 Sampling interval

equal or higher than the MinimumSamplingInterval if the Client subscribes to the Value Attribute . Clients should also be aware that the sampling by the OPC UA Server and the update
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.1.5 Queue parameters

sampling at a faster rate than the sampling interval to support other Clients ; the Client should only expect values at the negotiated sampling interval. The Server may deliver fewer values
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.1.6 Triggering model

concept. Figure 18 - Triggering model The triggering mechanism is a useful feature that allows Clients to reduce the data volume on the wire by configuring some items to sample frequently ... first notification is queued for the triggering item after the creation of the link. Clients create and delete triggering links between a triggering item and a set of items
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.2.1 Description

number of MonitoredItems each time may adversely affect the performance of the Server . Instead, Clients should add a complete set of MonitoredItems to a Subscription whenever possible. When a MonitoredItem ... description of the Access Type Parts. Clients may receive Notifications for added MonitoredItems before the CreateMonitoredItems Response is received. Clients set the ClientHandle for the MonitoredItem in the CreateMonitoredItems Request
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.13.6.1 Description

MonitoredItem that are in the process of being sent by the Subscription . Therefore, Clients may receive Notifications for the MonitoredItem after they have received a positive response that the MonitoredItem
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.14.1.1 Description

next publishing cycle. NotificationMessages are uniquely identified by sequence numbers that enable Clients to detect missed Messages . The publishing interval also defines the default sampling interval for its MonitoredItems . Subscriptions ... Publish requests per Session the Server shall support is defined in OPC 10000-7 . Clients are required to acknowledge NotificationMessages as they are received if the Publish response parameter availableSequenceNumbers
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.14.1.2 State table

Client , the Subscription assumes that the Client is no longer present, and terminates. Clients send Publish requests to Servers to receive Notifications . Publish requests are not directed
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.14.5.1 Description

Publish request before one of its outstanding Publish requests is returned from the Server . Clients can limit the size of Publish responses with the maxNotificationsPerPublish parameter passed to the CreateSubscription
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

5.14.5.2 Parameters

Client should not acknowledge sequence numbers. This information is for diagnostic purpose and Clients should log differences to the expected sequence numbers. moreNotifications Boolean A Boolean parameter with the following
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.1.2 Obtaining and installing an ApplicationInstanceCertificate

replacement before expiry of self-signed Certificates may be appropriate for a few Clients connected to one Server . In complex communication scenarios a central management of Certificates based
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.2.1 Overview

Overview Authorization Services provide Access Tokens to Clients on behalf of Users that they pass to a Server to be granted access to resources. In a basic model (as shown
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.2.2 Indirect handshake with an Identity Provider

Services (AS) provide access to identity providers which can validate the credentials provided by Clients . They then provide tokens which can be passed to a Server instead of the credentials
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.4 Auditing for Discovery Service Set

separated into two groups: Services that are called by OPC UA Clients and Services that are invoked by OPC UA Servers . The FindServers and GetEndpoints Services that are called ... Clients may generate audit entries for failed Service invocations. The RegisterServer Service that is invoked by OPC UA Servers shall generate audit entries for all new registrations and for failed
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.6 Auditing for Session Service Set

Events . See OPC 10000-3 for the definition of AuditCertificateEventType and its subtypes. For Clients , that support auditing, accessing the services in the Session Service Set shall generate audit entries
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.7 Auditing for NodeManagement Service Set

service failed. The additional parameters should include the details of the request. For Clients that support auditing, accessing the Services in the NodeManagement Service Set shall generate audit entries
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.8 Auditing for Attribute Service Set

Events of this type should include a description of why the Service failed. For Clients that support auditing, accessing the Write or HistoryUpdate services in the Attribute Service Set shall
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.9 Auditing for Method Service Set

detailed assignment of the SourceNode , SourceName and additional parameters. For Clients that support auditing, accessing the Method Service Set shall generate audit entries for both successful and failed invocations
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.5.10 Auditing for View, Query, MonitoredItem and Subscription Service Set

Events of this type should include a description of why the service failed. For Clients that support auditing, accessing the TransferSubscriptions Service in the Subscription Service Set shall generate audit
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.1 Redundancy overview

Redundancy overview OPC UA enables Servers, Clients and networks to be redundant. OPC UA provides the data structures and Services by which Redundancy may be achieved in a standardized manner ... Server Redundancy allows Clients to have multiple sources from which to obtain the same data. Server Redundancy can be achieved in multiple manners, some of which require Client interaction, others
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.2 RedundantServerSet Requirements

This is very important for Alarms & Conditions. For Cold, Warm, and Hot RedundantServerSets Clients shall be able to handle EventIds that are not synchronized. Following any Failover the Client ... SourceTimestamp and ServerTimestamp reported by all redundant Servers should match as closely as possible. Clients should favour the use of the SourceTimestamp . ContinuationPoints: Behaviour of continuation points does not change
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.3.1 Client behaviour

Transparent Redundancy setup example For transparent Redundancy , OPC UA provides data structures to allow Clients to identify which Servers are in the RedundantServerSet , the ServiceLevel of each Server, and which
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.2 ServiceLevel

Description 0-0 Maintenance The Failed Server is in maintenance sub-range. Therefore, new Clients shall not connect and currently connected Clients shall disconnect. The Server should expose a target ... time at which the Clients are able to reconnect. See EstimatedReturnTime defined in OPC 10000-5 for additional information. A Server that has been set to Maintenance is typically undergoing
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.3 Load balancing

available, the Servers in the RedundantServerSet can share the load generated by Clients by setting the ServiceLevel in the Healthy sub-range based on the current load. Clients are expected ... connect to the Server with the highest ServiceLevel . Clients shall not Failover to a different Server in the RedundantServerSet of Servers as long as the Server is in the Healthy
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.1 General

Failover mode in the ServerRedundancy Object defined in OPC 10000-5 . To enable Clients to connect to all Servers in the list, each Server in the list shall provide ... items. X Activate sampling on the Subscriptions . X X Activate publishing. X X X Clients communicating with a non-transparent RedundantServerSet of Servers require some additional logic to be able
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.4 Hot

find the highest ServiceLevel to achieve load balancing; this means that Clients should issue Service requests such as Browse , Read , Write to the Server with the highest ServiceLevel. Subscription related ... activities will need to be invoked for each connected Server . Clients have the following choices for implementing Subscription behaviour in a Hot Failover mode: The Client connects to multiple Servers
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.5 HotAndMirrored

Servers for status monitoring (to prevent excessive load on the Servers ). This mode allows Clients to fail over without creating a new context for communication. On a Failover the Client
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.5 Hiding Failover with a Server Proxy

functionality that needs to be designed into the Client and to enable simpler Clients to take advantage of non-transparent Redundancy . The Server proxy simply duplicates Subscriptions and modifications
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.3 Client Redundancy

Subscription lifetime is not tied to the Session in which it was created, backup Clients may use standard diagnostic information available to monitor the active Client's Session with ... mechanism for conveying the SessionId and SubscriptionIds from the active Client to the backup Clients , but as long as the backup Clients know the Client name of the active Client
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.8 Durable Subscriptions

Server restart would delete them. There are use cases where OPC UA Clients have no permanent network connection to the OPC UA Server or where reliable delivery of data changes
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.1 AdditionalParametersType

value of the additionalHeader field of the RequestHeader and ResponseHeader parameters. It allows Clients and Servers to pass additional named parameters with Service requests or responses. These named parameters
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.7.4.2 ElementOperand

index it is part of and it does not Reference a non-existent element. Clients shall construct filters in this way to avoid circular and invalid References . Servers should protect
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.9 ContinuationPoint

Service invocations, the ContinuationPoints are shared across all Session -less Service invocations from all Clients . The Server shall support at least the maximum number of ContinuationPoints it would allow
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.11.5 StatusCode assigned to a value

Rules The StatusCode indicates the usability of the value. Therefore, It is required that Clients minimally check the StatusCode Severity of all results, even if they do not check
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.22.1 Overview

have an associated MonitoringFilterResult structure which returns revised parameters and/or error information to Clients in the response. The result structures, when they exist, are described in the section that defines
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.22.4 AggregateFilter

period be used to compute the Aggregate . aggregateConfiguration Aggregate Configuration This parameter allows Clients to override the Aggregate configuration settings supplied by the AggregateConfiguration Object on a per monitored item
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.31 RegisteredServer

Client . isOnline Boolean True if the Server is currently able to accept connections from Clients . The Discovery Server shall return ApplicationDescriptions to the Client . The Server is expected to periodically ... Discovery Server. False if the Server is currently unable to accept connections from Clients . The Discovery Server shall NOT return ApplicationDescriptions to the Client. This parameter is ignored
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.38.1 General

additional information but do not affect the meaning of the StatusCode . All OPC UA Clients shall always check the StatusCode associated with a result before using it. Results that have ... associated results cannot be used. Reserved 11 Reserved for future use. All Clients should treat a StatusCode with this severity as "Bad". Reserved 29:29 Reserved
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.40.1 Overview

Overview The UserIdentityToken structure used in the Server Service Set allows Clients to specify the identity of the user they are acting on behalf of. The exact mechanism used
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.40.2.1 Overview

these secrets could be used by an attacker to gain access to the system. Clients shall validate the Server Certificate and ensure it is trusted before sending a UserIdentityToken encrypted
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.40.2.2 Legacy Encrypted Token Secret Format

then all bytes shall be zero. A Server shall check for padding added by Clients and ensure that all padding bytes are zeros. Servers shall reject UserIdentityTokens with invalid padding
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.40.5 X509IdentityTokens

Role . If the Server does not allow anonymous users, it should close the Session . Clients should renew the token with ActivateSession before the expiration time to avoid communication interruption
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.40.6 IssuedIdentityToken

Role . If the Server does not allow anonymous users, it should close the Session . Clients should renew the token with ActivateSession before the expiration time to avoid communication interruption
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

7.41 UserTokenPolicy

SecurityMode is None, SecurityPolicies based on ECC or RSA_DH are not allowed and Clients shall not use UserTokenPolicies that require encryption with these SecurityPolicies . RSA based SecurityPolicies are allowed
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.1 ServerType

Services to identify TargetNodes of References that reside in remote Servers . Clients may read the entire table or they may read individual entries in the table. The Server shall ... this table while any client has an open session to the Server , because clients may cache the server table . A Server may add entries to the server table even
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.10 NonTransparentNetworkRedundancyType

InstanceDeclarations of that Node. HasProperty Variable ServerNetworkGroups NetworkGroupDataType[] PropertyType Mandatory Conformance Units Redundancy Server Clients switching between network paths to the same Server behave the same as HotAndMirrored redundancy. Server
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.13 NamespaceMetadataType

publication date of the namespace version. This Property value can be used by Clients to determine the latest version if different versions are provided by different Servers when the ModelVersion
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.14 NamespacesType

NamespaceIndex of the QualifiedName and the namespace URI as name of the QualifiedName . Clients should not assume that all namespaces provided by a Server are present in this list
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.4.2 BaseEventType

unique EventId . It may do this, for example, by putting GUIDs into the ByteString. Clients can use the EventId to assist in minimizing or eliminating gaps and overlaps that ... severity levels across the 1 to 1 000 range in such a manner that clients can assume a linear distribution. For example, a client wishing to present five severity levels
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.10 OrderedListType

order is provided by the HasOrderedComponent References to the Objects . As not all Clients consider the order returned by the Browse Service (e.g. displaying the results in alphabetic order) each ... ordered List can change (e.g. new Objects added or removed). This allows Clients to subscribe to the Property or the GeneralModelChangeEvents , instead of polling Browse calls. Changes in the order
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

7.18 SelectionListType

indicating there are currently no valid values which can be written to the Variable . Clients should either subscribe to the Selections Property or read it just before use. The DataType
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

12.6 ServerState

process of shutting down. This ServerState is intended as an indication to Clients connected to the Server to orderly disconnect from the Server before the Server completes the shut down
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

12.10 ServerStatusDataType

actual shut down should be delayed for a configurable time if Clients are connected to the Server to allow these Clients an orderly disconnect. shutdownReason LocalizedText A localized text indicating
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

5.4.1 General

cases for the JSON encoding: cloud applications which consume PubSub messages and JavaScript Clients (JSON is the preferred serialization format for JavaScript). For the cloud application use case, the PubSub ... removed to meet the needs of cloud applications. Applications, such as JavaScript Clients , which use the DataEncoding for communication with other OPC UA applications require the artefacts. The CompactEncoding omits
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

6.2.2 Application Instance Certificate

profiles, the extendedKeyUsage shall specify serverAuth for Servers and shall specify clientAuth for Clients . The extendedKeyUsage should also specify clientAuth for Servers . For ECC profiles, serverAuth and clientAuth are optional
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

6.5.2.3 Access Tokens

Server does not allow anonymous users, it should close the Session immediately. Clients know when the Access Token will expire and should request a new Access Token and call ActivateSession
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

6.5.3.2 Authorization Code

Authorization Code The authorization code flow is available to Clients which allow interaction with a human user. The Client application displays a window with a web browser which sends
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

6.7.2.2 Message Header

after each restart. This ensures that a Server restart does not cause previously connected Clients to accidently 'reuse' SecureChannels that did not belong to them
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

7.1.2.6 ReverseHello Message

Server in the Hello Message . The encoded value shall be less than 4096 bytes. Clients shall return a Bad_TcpEndpointUrlInvalid error and close the connection if the length exceeds
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

7.1.3 Establishing a connection

usable network address. OPC 10000-7 defines Profiles for different name resolution protocols that Clients and Servers may support. If the Client creates the TransportConnection , the first Message sent shall ... Server is configured and enabled by an administrator to connect to one or more Clients . For each Client , the administrator shall provide an EndpointUrl which may be use to establish
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

7.4.1 Overview

shall be treated as a single SecureChannel that is shared by multiple Clients . Stacks shall provide a unique identifier for the SecureChannel which allows applications correlate a request with ... data and HTTPS with signing and encryption shall always be used. HTTPS allows Clients to have certificates; however, they are not required by the HTTPS transport. A Server shall allow
OPC-10000-6 – OPC Unified Architecture - Part 6: Mappings

7.5.3 Security

have the domain name as the common name component of the subject name however, Clients that are able to override the Certificate validation procedure can choose to accept Certificates with ... that is installed in the Trust List for the web browser. To support these Clients, a Server may use a TLS Certificate that does not conform to the requirements
OPC-10000-7 – OPC Unified Architecture - Part 7: Profiles

4.1 General

models can be referred to as features of a Server or Client . Servers and Clients need to be able to describe which features they support and wish to have certified
OPC-10000-7 – OPC Unified Architecture - Part 7: Profiles

4.8 Applications

subscribe for data, write to data and would support the DA data model. Clients should take into account the types of Servers and Server Profiles that they are targeted ... support. Some Servers might not support Subscriptions and Clients should be able to fall back to the Read Service. A special case is a generic Client that is designed
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

4 Concepts

links. OPC UA Data Access Servers provide one or more OPC UA Data Access Clients with transparent access to their automation data. The links to automation data instances are called ... broad range of different DataItems . Figure 1 - OPC DataItems are linked to automation data Clients can read or write DataItems , or monitor them for value changes. The Services needed
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

5.2 SemanticsChanged

defined in this standard change. The corresponding Properties are specified individually for each VariableType . Clients that use any of these Properties should re-read them before they process the data
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

5.3.2.2 BaseAnalogType

strongly recommended for Servers to support this Property . Without an InstrumentRange being provided, Clients will commonly assume the full range according to the DataType . The InstrumentRange Property can also
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

5.3.3.3 MultiStateDiscreteType

CLOSE" to 1 and "IN TRANSIT" to 2. Clients should be prepared to handle item values outside of the range of the list; and robust Servers should
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

5.3.3.4 MultiStateValueDiscreteType

this type. MultiStateValueDiscrete Variables expose the current integer notation in their Value Attribute . Clients will often read the EnumValues Property in advance and cache it to lookup a name ... Variables of MultiStateValueDiscreteType . These are Integers up to 64 Bits (signed and unsigned). Clients should be prepared to handle item values outside of the range of the list; and robust
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

5.6.4.1 General

defined in 5.6.4.4 , because it can be programmatically interpreted by generic OPC UA Clients . However, the EUInformation structure has been defined such that other standards bodies can incorporate their engineering
OPC-10000-8 – OPC Unified Architecture - Part 8: Data Access

6.5.1 HasEngineeringUnitDetails

ObjectType . The Reference has to change if the value (the concrete EngineeringUnit ) is changing. Clients can subscribe to the value and, in case of change, should rebrowse. The HasEngineeringUnitDetails
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

4.5 Condition state synchronization

Subscription . The currently existing state will not be reported. This means for example that Clients are not informed of currently Active Alarms until a new state change occurs. Clients ... general replay capability since the Server is not required to maintain an Event history. Clients request a Refresh by calling the ConditionRefresh Method . The Server will respond with a RefreshStartEventType
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

4.10 Condition instances in the AddressSpace

Reference to an instance of a LimitAlarmType . The availability of instances allows Data Access Clients to monitor the current Condition state by subscribing to the Attribute values of Variable Nodes
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.2 Two-state state machines

FalseState Property shall only exist on InstanceDeclarations . See Figure 9 for an illustration. Clients can use the Read Service to get the values of the TrueState and FalseState Property
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.5.4 Disable Method

Servers do not expose Condition instances in the AddressSpace. Therefore, all Servers shall allow Clients to call the Disable Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.5.5 Enable Method

Servers do not expose Condition instances in the AddressSpace. Therefore, all Servers shall allow Clients to call the Enable Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.5.6 AddComment Method

expose Condition instances in the AddressSpace. Therefore, all Servers shall also allow Clients to call the AddComment Method by specifying ConditionId as the ObjectId. The Method cannot be called with
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.5.7 ConditionRefresh Method

Notifier along with those being sent as part of the Refresh request. Clients shall check for multiple Event Notifications for a ConditionBranch to avoid overwriting a new state delivered together
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.5.8 ConditionRefresh2 Method

well-known NodeId of the ConditionType ObjectType . This Method is optional and as such Clients shall be prepared to handle Servers which do not provide the Method . If the Method ... notifier along with those being sent as part of the Refresh request. Clients shall check for multiple Event Notifications for a ConditionBranch to avoid overwriting a new state delivered together
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.7.2 AcknowledgeableConditionType

Server shall create a branch of the Condition instance as specified in 4.2 . Clients are expected to keep track of all ConditionBranches where AckedState /Id is False to allow acknowledgement
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.7.3 Acknowledge Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Acknowledge Method by specifying ConditionId as the ObjectId. The Method cannot ... Server is responsible to ensure that each Event has a unique EventId . This allows Clients to identify and acknowledge a particular Event Notification . The EventId identifies a specific Event Notification
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.7.4 Confirm Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Confirm Method by specifying ConditionId as the ObjectId. The Method cannot ... Server is responsible to ensure that each Event has a unique EventId . This allows Clients to identify and confirm a particular Event Notification . The EventId identifies a specific Event Notification
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.2 AlarmConditionType

Alarm on all systems (screens) that it is being reported on. Not all Clients will make use of this StateMachine , but it allows multiple Clients to synchronize audible Alarm states
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.5 Reset Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Reset Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.7 Silence Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Silence Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.8 Suppress Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Suppress Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.10 Unsuppress Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the Unsuppress Method by specifying ConditionId as the ObjectId. The Method cannot
OPC-10000-9 – OPC Unified Architecture - Part 9: Alarms & Conditions

5.8.12 RemoveFromService Method

some Servers do not expose Condition instances in the AddressSpace. Therefore, Servers shall allow Clients to call the RemoveFromService Method by specifying ConditionId as the ObjectId. The Method cannot