# Constraint references

**URL:** https://discourse.openehr.org/t/constraint-references/12199
**Category:** Technical (archive)
**Created:** [22 November 2006 09:24 UTC](https://discourse.openehr.org/t/constraint-references/12199 "2006-11-22T09:24:31Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Mattias\_Forss1](https://discourse.openehr.org/letter_avatar_proxy/v4/letter/m/e9c0ed/32.png) [@Mattias\_Forss1](https://discourse.openehr.org/u/Mattias_Forss1)
#### Post date: [22 November 2006 09:24 UTC](https://discourse.openehr.org/t/constraint-references/12199/1 "2006-11-22T09:24:31Z")

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Hi all,

I’m wondering what the difference is between a CONSTRAINT\_REF and a C\_DV\_CODED\_TEXT that has the query attribute set? The descriptions of the two are the following:

CONSTRAINT\_REF class description:  
Reference to a constraint described in the same archetype, but outside the main constraint structure. This is used to refer to constraints expressed in terms of external resources, such as constraints on terminology value sets.

Description of query attribute of C\_DV\_CODED\_TEXT:  
Constraint in terms of an abstract query expression to be addressed to a terminology server.

Is there a syntactic difference between the two in ADL?

Mattias

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### Author: ![Sam](https://discourse.openehr.org/letter_avatar_proxy/v4/letter/s/5f9b8f/32.png) [@Sam](https://discourse.openehr.org/u/Sam)
#### Post date: [17 December 2006 23:06 UTC](https://discourse.openehr.org/t/constraint-references/12199/2 "2006-12-17T23:06:37Z")

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C\_CODED\_TEXT at least… Sam

Rong Chen wrote: