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Deployment OPC UA
Basics OPC UA > Information modeling
Node classes
Node attributes
OPC UA services
Basic service sets
186
n
In an information model, the content of the address space of the OPC UA server is
described.
n
The Information models are structured in layers. Each higher-order type is based on
certain basic rules. Thus, clients who only know the basic rules can still edit complex
information models, e.g. navigate through the address space and read or write data
variables.
n
In the address space, all information is represented by Nodes, which are intercon-
nected via references.
A node is always an instance of a NodeClass.
n
OPC UA offers basic services such as data exchange or navigation through the
n
address space. The services are grouped in Service Sets.
The following NodeClasses are defined in the OPC UA specification:
Variable - class of variables
n
n
Method - class of functions
n
Object - class of objects
n
View - Class of view of a subset of nodes
n
DataType - Class of the data types of the value of a variable
n
VariableType - Class of the data types of a variable
n
ObjectType - class of object types
n
ReferenceType - class of reference types
Each node consists of attributes and references. Some attributes may also be optional.
The following attributes of each NodeClass must be published:
n
NodeID - Unique identifier of a nodes in the address space
n
NodeClass - class of node instance
n
BrowseName - name of the node in plain text
n
DisplayName - display name of the Node for the user
Description - Description of the node (optional)
n
n
OPC UA services are abstract descriptions defined by request and response mes-
sages.
n
The available services of an OPC UA server are defined in the server profile and
grouped together in service sets.
n
Discovery Service Set
–
Services for discovering existing servers and endpoints.
n
SecureChannel Service Set
–
Services for opening and closing secure communication channels.
n
Session Service Set
–
Services for the client to create and manage a session.
n
NodeManagement Service Set
–
Services for creating and deleting nodes and references.
n
View Service Set
–
Services for the client to navigate in the address space or in the view.
n
Query Service Set
–
Services for search queries in the address space.
n
Attribute Service Set
–
Services for accessing attributes of nodes.
n
Method Service Set
–
Service for calling a method of an object.
VIPA System SLIO
HB300 | CPU | 013-CCF0R00 | en | 19-30
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