# Correct way to approch Siemens UDT's and big data structures **URL:** \ **Category:** Ignition\ **Tags:** perspective, ignition81\ **Created:** [March 18, 2024, 5:03pm UTC](https://forum.inductiveautomation.com/t/correct-way-to-approch-siemens-udts-and-big-data-structures/87505 "2024-03-18T17:03:30Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [March 18, 2024, 5:07pm UTC](https://forum.inductiveautomation.com/t/correct-way-to-approch-siemens-udts-and-big-data-structures/87505/2 "2024-03-18T17:07:20Z")
Hmm, I have no idea if this "drag to a custom property" thing is supposed to work. I honestly don't know what that does on the backend and what happens when you modify that property. The traditional setup for structures from OPC UA servers is to create a set of matching derived tags that use `jsonGet`/`jsonSet` expressions for each of the members, and then write to the derived tags, which in turn write to the document tag for the base structure. > [@OPC UA struct data type?](https://forum.inductiveautomation.com/t/opc-ua-struct-data-type/26905/2): > > You can take advantage of reading whole structs in OPC UA servers as of Ignition 7.9.12 and 8.0.0. When you bring the tag in you’ll notice Ignition presents a JSON value. The strategy here is a little involved but it works. For each of the UDTs you’ll be subscribing to in the PLC you make a corresponding UDT in Ignition. It should have a “Source” OPC tag member that will correspond to the Node with the struct value in the server and as a result have a JSON value in Ignition. Then for each memb… --- _[View the full topic](https://forum.inductiveautomation.com/t/correct-way-to-approch-siemens-udts-and-big-data-structures/87505)._