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Analogy to DataSet
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Aydin Homay
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07/14/2021 - 05:53
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Hi,

I have the following data structure in my system, call it PV: 

  • PvName
  • DataType (Boolean , int, string, double, array (one diamentional), etc) 
  • ServerTimeStamp
  • Value
  • Unit                   
  • Size (size of data stored in the value field)
  • quality
  • alarm

Now I wanna create DataSet for the following structure on the PubSub communication model. I came up with the following structure: 

<Fields>
  <FieldMetaData>
     <Name>DSS:FDS_SVC:CON_FDS_SVC</Name>
     <Description>
        <Locale i:nil=”true” />
        <Text>FDS SVC Client Connection</Text>
     </Description>
     <FieldFlags>0</FieldFlags>
     <BuiltInType>6</BuiltInType>
     <DataType>
        <Identifier>i=6</Identifier>
     </DataType>
     <ValueRank>-1</ValueRank>
     <ArrayDimensions />
     <MaxStringLength>0</MaxStringLength>
   <DataSetFieldId>
<String>1bc6c8dd-724d-4f39-884c-630175bf37df</String>
</DataSetFieldId>
<Properties>
   <KeyValuePair>
     <Key>
        <NamespaceIndex>0</NamespaceIndex>
        <Name>Unit</Name>
     </Key>
   <Value>
      <Value>
      <String xmlns=”https://opcfoundation.org/UA/2008/02/Types.xsd” />
   </Value>
   </Value>
</KeyValuePair>
<KeyValuePair>
<Key>
<NamespaceIndex>0</NamespaceIndex>
<Name>Alarm</Name>
</Key>
<Value>
<Value>
<String xmlns=”https://opcfoundation.org/UA/2008/02/Types.xsd”>HH</String>
</Value>
</Value>
</KeyValuePair>
</Properties>
</FieldMetaData>
</Fields>

Now I have two questions:

1- Does the analogy created by me correct? Does it make sense? 

2- When I change the value I only receive the value on the subscriber side not the properties. Why is that? 

 

Thank you for your support. 

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Randy Armstrong
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07/14/2021 - 08:08
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The properties are reported with the metadata.

If you want them in every message you need to create a field for them.

ServerTimeStamp, Value and quality (a.k.a. StatusCode) are part of the DataValue and can set the DataSetFieldContentMask to include information.

The generic word “alarm” should be replaced with something more specific.

i.e. LevelAlarmMessage.

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Aydin Homay
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07/14/2021 - 08:27
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So you mean alram (LevelAlarmMessage) and Unit they need to be independent Fields? If I want to receive them every time that the value of my dataset (DSS:FDS_SVC:CON_FDS_SVC) is changing.

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Randy Armstrong
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07/14/2021 - 09:04
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You can configure delta frames so the metadata does not need to be sent every time if it is not changing.

But yes, you would need more fields if you want to receive that information inline with the value.

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