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Dynamic tag addressing
January 23, 2014
9:48, EET
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Roger
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January 14, 2014
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I’m new to OPC UA technology so this might be a stupid question but I’m using KEPServerEX5 which has the concept of dynamic tag addressing which they define as follows:
Dynamic Tag addressing is a second method of defining tags that allows users to define tags only in the client application. As such, instead of creating a tag item in the client that addresses another tag item created in the server, users only need to create tag items in the client that directly accesses the device driver’s addresses. On client connect, the server will create a virtual tag for that location and will start scanning for data automatically.

An example of such an address would be “MyChannel.MyPLC.DB40,B0”

Is it possible to use this type of addressing with OPC UA?

As I understand it I have to browse to a node first to be able to read/write from/to it, but since it does no exist until it has been accessed I’m lost Smile

January 23, 2014
10:13, EET
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Jouni Aro
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I am not quite sure about the Kepware implementation, but I would imagine that the address would be used to define the NodeId of the tag.

Typically, you do browse first to find the nodes that you wish to read or monitor, but that is not actually necessary. Browsing provides you the NodeId of the tag, but if you can define the NodeId without browsing it will work as well.

The NodeId is defined with a NamespaceIndex and an ID (in various alternative formats). You will need to find out the NamespaceIndex that the nodes are in and maybe use the tag address as the ID in string format.

The NamespaceIndex refers to the position of the respective NamespaceURI in the NamespaceArray of the server. In the Java SDK, you can use the UaClient.getNamespaceTable() object to convert between the known NamespaceURI and the respective NamespaceIndex.

I suggest that you check the Kepware documentation for details on how the tag should be addressed and if this is the correct way to do it.

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