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I'm wondering why the spec for SimpleAttributeOperand uses a browsePath list and not just a NodeId as the parameter.

From my understanding, NodeId would uniquely identify a node object but instead, we use a browse path list as specified for SimpleAttributeOperand which would lead to possible duplicates. In other words, two nodes can have the same browse name.

Am I correct in thinking this is an issue?

dtc
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1 Answers1

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SimpleAttributeOperand is typically used to define the fields of an EventFilter.

The BrowsePath defines an element of the event relative to itself. You define, for example, that you wish to monitor all events from the server, and for each of them, you wish to get the Message. Alarms use nodes that contain the Message, but it's a different node for each alarm - and simple events don't define any nodes in the address space. So you don't want to use NodeIds for defining that, in practice.

Jouni Aro
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  • Well I think I can't use NodeIds because it's not part of the spec so the server isn't going to accept it. I'm wondering why the spec was designed this way because...see my post again. – dtc Jun 10 '22 at 18:45
  • The fields in the filter define relative nodes, not absolute. That's why. – Jouni Aro Jun 14 '22 at 10:05
  • that tells me what the spec does which i already know, not why it was designed that way. and aside from that, the actual question is asking if a duplicate node is a potential problem here. – dtc Jun 23 '22 at 17:43