Overview
The OPC UA Services are defining the data communication on application level. Services are methods used by an OPC UA client to access the data of the Information Model provided by an OPC UA server. Similar to Classic OPC, where the OPC specifications just defined Application Programming Interface (APIs) bet?ween applications, the Services define the communication interface between UA applications. The definition of the Services is independent of the transport protocol and the programming environment that is used to develop an OPC UA application. This is the fundamental difference to Classic OPC where the definition of the APIs was bound to a specific transport mechanism – Microsoft Component Object Model (COM).
The independence of the transport protocol and the programming environment requires an abstract definition of the Services. This abstract definition [UA Part 4] can be applied to different transport mechanisms (see Chap.6) defining the representation of the Services on the wire [UA Part 6] and to different implementations of the transport mechanisms in OPC UA Stacks (see Sect. 6.5) in different programming languages. The language specific APIs for the application development are defined by the OPC UA Stacks based on the abstract UA Service definition.
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Notes
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For example devices connected to the server by an interrupted network.
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Combination of StatusCode and DiagnosticInformation.
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An EventNotifier is an Object where the SubscribeForEvents flag is set in the EventNotifier Attribute.
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An EventNotifier is an Object where the SubscribeForEvents flag is set in the EventNotifier Attribute.
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SimpleAttributeOperand containing similar information like a SelectClause element.
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Comparable to interface methods in COM.
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© 2009 Springer-Verlag Berlin Heidelberg
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Mahnke, W., Leitner, SH. (2009). Services. In: OPC Unified Architecture. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-68899-0_5
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DOI: https://doi.org/10.1007/978-3-540-68899-0_5
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