# Occurrences on Top level element
**URL:** https://discourse.openehr.org/t/occurrences-on-top-level-element/14362
**Category:** Clinical (archive)
**Created:** [27 October 2017 22:47 UTC](https://discourse.openehr.org/t/occurrences-on-top-level-element/14362 "2017-10-27T22:47:33Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@leonardo\_ornelas](https://discourse.openehr.org/u/leonardo_ornelas)
#### Post date: [27 October 2017 22:47 UTC](https://discourse.openehr.org/t/occurrences-on-top-level-element/14362/1 "2017-10-27T22:47:33Z")
Hello, my name is Leonardo Ornelas, this is my first message for this mail list. Maybe somebody could take my doubts. I’m working on a project that follows some parts of openEHR. I did an adl-core implementation on nodejs. This version makes the parser from adl to json, supports flattener of archetypes and generation of operational templates, as well as the generation of a hierarchical model of RM from Archetype / OPT. There is a person in the team in charge of creating some templates and archetypes for our needs, which led to a questioning about occurrences that he could not answer. I looked in the document but could not find it on. I wonder if in the RM model it is possible to have occurrences of a element that is root? Eg. If a CLUSTER is the first element of an archetype that cluster could have occurrence 0 .. \* or 1 .. \*.
Could the following ADL be valid?
…
definition
EVALUATION [id1.1] matches occurrences matches {0..2} matches {
…
In that case, in the RM model, when in the form add a new element, could I have an EVALUDATION with the same archetype\_node\_id?
Thanks in advance.
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### Author:  [@system](https://discourse.openehr.org/u/system)
#### Post date: [29 October 2017 11:55 UTC](https://discourse.openehr.org/t/occurrences-on-top-level-element/14362/2 "2017-10-29T11:55:05Z")
Hi Leonardo
I think such a constraint usually belongs in the container. Do you have an example?
Cheers, Sam
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### Author:  [@system](https://discourse.openehr.org/u/system)
#### Post date: [30 October 2017 08:14 UTC](https://discourse.openehr.org/t/occurrences-on-top-level-element/14362/3 "2017-10-30T08:14:46Z")
Sam is right. The occurrences of an archetype root is always {1..1}. In the container of that archetype (an archetype slot) you can redefine those occurrences.