How things work - ignition opc tags

hi all
Ignition has opc tags and non opc tags ( memory, expression, …) - in order to use opc tags from other OPC UA server they have to be copied to ignition during opc browsing. I heard that some other scada vendors make all tags opc based and also copying opc tags in browser window in not necessary. Just wonder what are benefits of each solution and maybe somebody knows why ignition chose tag database aproach? Just trying to understand bit deeper

Hey hewking32,

When you say copying OPC tags to the window, do you mean going to the tag browser and adding tags from a device (Ignition) vs. having all available tags showing automatically on the tag browser?

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thanks for reply
yes you described “copying opc” tags exactly how i meant and thats how ignition is. But opposite solution i would describe different eg i heard that rockwell factory talk does not need copying opc tags as they are used can be used directly from the source. So you could open such project and see no tags except internal tags… Just wonder why things are as they are

Nearly every OPC subscription is a drag on the comms to a PLC. Deliberately making OPC tags helps control/constrain that problem. Also, it is rare for a PLC's internal tag architecture to be organized for effective page/view/window/template reusability. Making Ignition tags with a repeating folder structure (best with UDTs) is necessary for large scale component reusability. Ignition tags do not have to and usually should not follow the same architecture as the target PLC.


thanks for your help