# Dynamic OPC Path referencing an internal Query Tag within UDT

**URL:** <https://forum.inductiveautomation.com/t/dynamic-opc-path-referencing-an-internal-query-tag-within-udt/113951>\
**Category:** Ignition\
**Tags:** ignition81\
**Created:** [February 13, 2026, 6:42am UTC](https://forum.inductiveautomation.com/t/dynamic-opc-path-referencing-an-internal-query-tag-within-udt/113951 "2026-02-13T06:42:23Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Aiasa21](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Aiasa21](https://forum.inductiveautomation.com/u/Aiasa21)\
**Post date:** [February 13, 2026, 6:42am UTC](https://forum.inductiveautomation.com/t/dynamic-opc-path-referencing-an-internal-query-tag-within-udt/113951/1 "2026-02-13T06:42:23Z")

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Hi everyone,

I’m looking for a way to streamline my UDT definition and I’ve hit a bit of a roadblock regarding tag referencing.

Inside my UDT, I have a folder named **`Position_ID`** which contains a Query Tag named **`Extruder`**. This query automatically retrieves the correct identifier from a database based on the `{RootInstanceName}` of the UDT.

I have an OPC Tag within the same UDT that requires a dynamic OPC Path. This path needs to be built using the value returned by the **`Extruder`** Query Tag.

How can I reference the value of the internal **`Extruder`** tag directly within the OPC Path configuration?

I want to avoid adding a manual UDT Parameter just to duplicate a value that is already being fetched by the Query Tag. I've tried a few syntax variations, but the OPC Path doesn't seem to resolve when pointing to a tag value instead of a parameter.

Thanks!

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**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [February 13, 2026, 2:02pm UTC](https://forum.inductiveautomation.com/t/dynamic-opc-path-referencing-an-internal-query-tag-within-udt/113951/2 "2026-02-13T14:02:14Z")

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> [@Aiasa21](#):
>
> How can I reference the value of the internal **`Extruder`** tag directly within the OPC Path configuration?

You cannot. Tag properties within UDTs only support parameter binding. The closest you can come would be to place a `valueChange` script on the query tag that writes the parameter.

I would encourage you to avoid query tags in UDTs, though. When needed for configuration, you should simply arrange for the tag configuration to get the right parameters through some design automation, not runtime. When used at runtime for message lookups or other truly dynamic purpose, they tend to blow up ones database.

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**Author:** ![Aiasa21](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Aiasa21](https://forum.inductiveautomation.com/u/Aiasa21)\
**Post date:** [February 13, 2026, 3:43pm UTC](https://forum.inductiveautomation.com/t/dynamic-opc-path-referencing-an-internal-query-tag-within-udt/113951/3 "2026-02-13T15:43:28Z")

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Thank you for the answer and the suggestion, I will treasure it.