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Use Case |
Read offline parameters |
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Description |
A software or user requests device parameter (the last set values) from a DTM. The OPC UA client collects this information by reading device parameter from the offline set provided according to the FDT OPC UA information model. |
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Stakeholder |
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Preconditions |
Device node is available in OPC UA Server and the Client already knows the ParameterIds of the Parameters to read (may have been retrieved according to use case B4.2). |
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Post conditions |
Client knows the current value of device parameters |
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Actors |
Engineer, Expert, Observer, Operator |
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Trigger |
Whenever the data is needed |
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Frequency |
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Description |
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Step |
Action |
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Preparation |
The OPC Client selects the respective device node and the parameter set of the device. |
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1 |
OPC Client executes Read-Service (one or multiple times) with the list of identifiers for the respective device parameters (list of ParameterIds) and the list of AttributeIds for Value and (at least once) for DateType. |
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2 |
OPC Server retrieves the requested attributes (e.g. value) of the parameter which are specified in the Read-Request from the DTM (instance data set) and returns them to the client. |
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5 |
OPC Client displays the parameter value (or uses it otherwise). |
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Exceptions |
Step 1, The specified parameter does not exist in the device. |
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Requirements |
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Notes |
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Open Issues |
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