Glossary

The collection of information that an OPC Unified Architecture Server makes visible to its Clients. See section Address Space for a description of the contents and structure of the server Address Space.

A type of Event associated with a state condition that typically requires acknowledgement. See section Alarms and Conditions for a description of Alarms.

A primitive characteristic of a Node. All Attributes are defined by OPC Unified Architecture, and may not be defined by Clients or Servers. Attributes are the only elements in theAddress Spacepermitted to have data values.

A digitally signed data structure that describes capabilities of a Client or Server.

A software application that sends Messages to OPC Unified Architecture Servers conforming to the Services specified in this set of specifications.

A layered set of software modules between the application and the hardware that provides various functions to encode, encrypt and format a Message for sending, and to decode, decrypt and unpack a Message that was received.

Data that is composed of elements or more than one primitive data type, such as a structure.

A generic term that is an extension to an Event. A Condition represents the conditions of a system or one of its components and always exists in some state.

The data type dictionary is represented as a Variable of type DataTypeDictionaryType in the Address Space, the description about the data types is contained in its Value attribute.

The process by which OPC Unified Architecture Client obtain information aboutOPC Unified ArchitectureServers, including endpoint and security information.

A generic term used to describe an occurrence of some significance within a system or system component.

A type defined in or derived from a type defined in section Standard Event Types.

A special Attribute of a Node that signifies that a Client may subscribe to that particular Node to receive Notifications of Event occurrences.

Client without any initial knowledge about available nodes class.

An organizational framework that defines, characterizes and relates information resources of a given system or set of systems. The core address space model supports the representation of Information Models in theAddress Space. For more information see <link xlink:href="3f999f23-4ad7-46a4-80dd-ab33729d5f49" />.

The data unit conveyed between Client and Server that represents a specific Service request or response.

A callable software function.

A Client-defined entity in the Server used to monitor Attributes or EventNotifiers for new values or Event occurrences and generate Notifications for them.

The indexes into the NamespaceArray table.

The fundamental component of an Address Space.

The class of a Node in an Address Space. NodeClasses define the metadata for the components of theOPC Unified ArchitectureObject Model. They also define constructs, such as Views, that are used to organize theAddress Space.

The generic term for data that announces the detection of an Event or of a changed Attribute value. Notifications are sent in NotificationMessages.

A Message published from a Subscription that contains one or more Notifications.

A Node that represents a physical or abstract element of a system. Objects are modelled using the OPC Unified Architecture Object Model. Systems, subsystems and devices are examples of Objects. An Object may be defined as an instance of an ObjectType.

A synonym for Object. Not all Objects are defined by ObjectTypes.

A Node that represents the type definition for an Object.

A specific set of capabilities, described in section Profiles, to which a Server may claim conformance. Each Server may claim conformance to more than one Profile.

An executable Object that, when invoked, immediately returns a response to indicate that execution has started, and then returns intermediate and final results through Subscriptions identified by the Client during invocation.

An explicit relationship (a named pointer) from one Node to another. The Node that contains the Reference is the source Node, and the referenced Node is the target Node. All References are defined by ReferenceTypes.

A Node that represents the type definition of a Reference. The ReferenceType specifies the semantics of a Reference. The name of a ReferenceType identifies how source Nodes are related to target Nodes and generally reflects an operation between the two, such as “A Contains B”.

The beginning or top Node of a hierarchy. The RootNode of the OPC Unified ArchitectureAddress Space is defined in Part 5:.

A software application that implements and exposes the Services specified in this set of specifications.

A Client-callable operation in an OPC Unified Architecture Server. Services are described in section Services. A Service is similar to a method call in a programming language or an operation in a Web services WSDL contract.

A group of related Services.

A logical long-running connection between a Client and a Server. A Session maintains state information between Service calls from the Client to the Server.

A Client-defined endpoint in the Server, used to return Notifications to the Client. Generic term that describes a set of Nodes selected by the Client (1) that the Server periodically monitors for the existence of some condition, and (2) for which the Server sends Notifications to the Client when the condition is detected.

A Variable is a Node that contains a value.

A specific subset of the Address Space that is of interest to the Client.

Alarms and Events

Application Programming Interface

Component Object Model

Data Access

Distributed Control System

Data Exchange

Historical Data Access

Human-Machine Interface

Lightweight Directory Access Protocol

Manufacturing Execution System

OPC Foundation (a non-profit industry association)

Programmable Logic Controller

Supervisory Control And Data Acquisition

Simple Object Access Protocol

Unified Architecture

Universal Description, Discovery and Integration

Unified Modelling Language

Web Services Definition Language

Extensible Mark-up Language