OPC UA Part 1 - Overview and Concepts 1.02 Specification(19)

OPC UA Specification Part1 OverView and Concepts

Release 1.02 11 OPC Unified Architecture, Part 1

5.4.1.4 Transport security

OPC UA security complements the security infrastructure provided by most web service capable platforms.

Transport level security can be used to encrypt and sign Messages. Encryption and signatures protect against disclosure of information and protect the integrity of Messages. Encryption capabilities are provided by the underlying communications technology used to exchange Messages between OPC UA applications. Part 7 defines the encryption and signature algorithms to be used for

a given Profile.

5.4.2 Integrated AddressSpace model

The set of Objects and related information that the OPC UA Server makes available to Clients is referred to as its AddressSpace. The OPC UA AddressSpace represents its contents as a set of Node s connected by References.

Primitive characteristics of Node s are described by OPC-defined Attributes. Attributes are the only elements of a Server that have data values. Data types that define attribute values may be simple or complex.

Node s in the AddressSpace are typed according to their use and their meaning. NodeClasses define the metadata for the OPC UA AddressSpace. Part 3 defines the OPC UA NodeClasses.

The Base NodeClass defines Attributes common to all Node s, allowing identification, classification and naming. Each NodeClass 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 for all Servers. Although Node s in the AddressSpace are typically accessible via the hierarchy, they may have References to each other, allowing the AddressSpace to represent an interrelated network of Node s. The model of the AddressSpace is defined in Part 3.

OPC UA Servers may subset the AddressSpace into Views to simplify Client access. Clause 6.3.3.3 describes AddressSpace Views in more detail.

5.4.3 Integrated object model

The OPC UA Object Model provides a consistent, integrated set of NodeClasses for representing Objects in the AddressSpace. This model represents Objects in terms of their Variables,Events and Methods, and their relationships with other Objects. Part 3 describes this model.

The OPC UA object model allows Servers to provide type definitions for Objects and their components. Type definitions may be subclassed. They also may be common or they may be system-specific. ObjectTypes may be defined by standards organizations, vendors or end-users. This model allows data, Alarms and Events, and their history to be integrated into a single OPC UA Server. For example, OPC UA Servers are able to represent a temperature transmitter as an Object that is composed of a temperature value, a set of alarm parameters, and a corresponding set of alarm limits.

5.4.4 Integrated services

The interface between OPC UA Clients and Servers is defined as a set of Services. These Services are organized into logical groupings called Service Sets. Service Sets are discussed in Clause 7 and specified in Part 4.