# Constraints on Issuer and assigner in DV_Identifier

**Category:** [LinkEHR](https://discourse.openehr.org/c/linkehr/38)
**Created:** 2025-03-03 16:03 UTC
**Views:** 43
**Replies:** 2
**URL:** https://discourse.openehr.org/t/constraints-on-issuer-and-assigner-in-dv-identifier/6509

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## Post #1 by @birger.haarbrandt

Hi everybody,

I'm currently working on a template which stores implant data. There is a code called UDI (https://health.ec.europa.eu/medical-devices-topics-interest/unique-device-identifier-udi_en) to identify the medical device. There is only a small list of eligible issuers for the UDIs and therefore I would like to put a constraint on mentioned field(s).

To me it looks like setting the constraints is not supported by the UI in LinkEHR or Archetype Designer. Also, it would be nice to be able to provide a Regex as part of the validation. So I wanted to check if this a correct observation that this is supported by the AM but not the tools at the moment.

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## Post #2 by @yampeku

LinkEHR probably does not support this in the openEHR specific editor, but you should be able to define that regex string constraint in the general tree editor
![imagen|477x297](upload://871RQ5peJPAqzm45LhxLEonkTPS.png)

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## Post #3 by @birger.haarbrandt

Perfect, thanks a lot, I indeed looked in the wrong place!

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**Canonical:** https://discourse.openehr.org/t/constraints-on-issuer-and-assigner-in-dv-identifier/6509
**Original content:** https://discourse.openehr.org/t/constraints-on-issuer-and-assigner-in-dv-identifier/6509