# AQL query to archetype and it's specializations in slot

**Category:** [Clinical (archive)](https://discourse.openehr.org/c/clinical-archive/153)
**Created:** 2010-06-28 03:59 UTC
**Views:** 1
**Replies:** 1
**URL:** https://discourse.openehr.org/t/aql-query-to-archetype-and-its-specializations-in-slot/14581

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## Post #1 by @user3

Hi!

I have an archetype 'A' with slot named 'Slot In A'.
There is constraint for possible archetypes for this slot: "B and specializations of B".

I know that in archetype B (and in all of it's specializations) there is field 'at0003' named 'Field In B'

I know only about B and particular clients has their own independent specializations 'B-spec'.

Now I want to build a query like this:

...[openEHR-EHR-CLUSTER.a.v1] /items[openEHR-EHR-CLUSTER.b.v1] / items[at0003]/value

And I want something like "Archetype of this type and it's specializations" instead of just this "items[openEHR-EHR-CLUSTER.b.v1]".

The question is: how :-)

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## Post #2 by @system

Hi Igor,

AQL allows string RegEx pattern in an archetype predicate. RegEx pattern needs to be enclosed by ‘{/’ RegEx ‘/}’. For your scenario, the AQL may include something like:

...[openEHR-EHR-CLUSTER.a.v1] /items[{/openEHR-EHR-CLUSTER\.b(-[a-zA-Z0-9])*\.v1/}] / items[at0003]/value

Or something like the one below. The expression below is for retrieving both element [at0003] instance value and the specialization of this element if the specialized archetype has specialization of element at0003 (such as at0003.1):

...[openEHR-EHR-CLUSTER.a.v1] /items[{/openEHR-EHR-CLUSTER\.b(-[a-zA-Z0-9])*\.v1/}] / items[{/at0003([0-9.]+)*/}]/value

Hope this helps. Please let me know if you have more questions.

Regards,

Chunlan

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**Canonical:** https://discourse.openehr.org/t/aql-query-to-archetype-and-its-specializations-in-slot/14581
**Original content:** https://discourse.openehr.org/t/aql-query-to-archetype-and-its-specializations-in-slot/14581