Can we have duplicate name in Payload of a NetworkMessage|OPC UA Standard|Forum|OPC Foundation

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Can we have duplicate name in Payload of a NetworkMessage
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Karthickperumal Perumal
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07/20/2021 - 20:23
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Hi All,

I need to send same Tags with different time stamp in a Single Network message.

As specification says, the Payload object is a name-value pair, here the name is a Tag/node name in the Dataset.

Is it valid to have duplicate name with different timestamp in a Network message?

Please share your inputs on this.

Thank you in advance.

https://reference.opcfoundatio.....3/#7.2.3.3

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Randy Armstrong
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07/21/2021 - 12:20
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You can't have duplicate names in JSON payloads because they are a JSON object.

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Karthickperumal Perumal
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07/21/2021 - 18:33
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Thank you Randy.

The use case which I am trying to address here is, we have Publisher components which fetch data from the UA Server and sent to Mqtt broker.

So, if the publisher is subscribed to a server monitored item, where Queue size is greater than 1 (Say 5).

For every publishing interval, Publishing response may have 5 values for the monitored item.

How to send all the 5 values received from the server, in the Payload to the Broker.

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Randy Armstrong
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07/22/2021 - 06:34
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Each NetworkMessage can have multiple DataSetMessages.

Create a DataSetMessages for each sampling interval.

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Karthickperumal Perumal
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07/25/2021 - 18:54
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Hi Randy,

Thanks for your Inputs. 

So i created multiple DatasetMessage for a Tag/Item for every Sampling Interval. The Network Message looks as given below:

{"MessageId":"1287f24d-8229-4580-874f-0eaf142526f9","MessageType":"ua-data","PublisherId":"Publisher","DataSetClassId":"6a4379ac-0adb-4000-8b7e-b57eaca01826",
"Messages":{"DataSetWriterId":1,"SequenceNumber":15,"MetaDataVersion":{"MajorVersion":1,"MinorVersion":1},"Payload":{"DataSetId":{"Value":{"Type":12,"Body":"DataSetId#01"},"SourceTimestamp":"2021-07-26T01:30:40.1811213Z","ServerTimestamp":"2021-07-26T01:30:40.181122Z"},"NS4|Numeric|1003":{"Value":{"Type":4,"Body":9},"SourceTimestamp":"2021-07-26T01:29:56.4537117Z","ServerTimestamp":"2021-07-26T01:29:56.5847112Z"}}},
"Messages":{"DataSetWriterId":1,"SequenceNumber":16,"MetaDataVersion":{"MajorVersion":1,"MinorVersion":1},"Payload":{"NS4|Numeric|1003":{"Value":{"Type":4,"Body":10},"SourceTimestamp":"2021-07-26T01:29:59.0757308Z","ServerTimestamp":"2021-07-26T01:29:59.184747Z"}}},
"Messages":{"DataSetWriterId":1,"SequenceNumber":17,"MetaDataVersion":{"MajorVersion":1,"MinorVersion":1},"Payload":{"NS4|Numeric|1003":{"Value":{"Type":4,"Body":11},"SourceTimestamp":"2021-07-26T01:30:01.3107239Z","ServerTimestamp":"2021-07-26T01:30:01.3847107Z"}}}}

The problem here is, the  JSON validator is failing, with Error "Duplicate key 'Messages'.

Any inputs on this?

Thank you.

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Randy Armstrong
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07/25/2021 - 19:26
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Make sure the message complies with:

https://reference.opcfoundatio.....t14/7.2.3/

Should be a JSON array not a JSON object.

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Zbynek Zahradnik
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07/25/2021 - 21:59
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Here is (my) tool that will show you how the possible formats should look like: OPC UA PubSub Formatter, https://kb.opclabs.com/Tool_Do....._Formatter .

Best regards

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