# Question about occurrences and cardinality values in the Blood Pressure archetype

**Category:** [Clinical (archive)](https://discourse.openehr.org/c/clinical-archive/153)
**Created:** 2011-08-02 10:46 UTC
**Views:** 1
**Replies:** 6
**URL:** https://discourse.openehr.org/t/question-about-occurrences-and-cardinality-values-in-the-blood-pressure-archetype/15081

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## Post #1 by @Seref

Greetings,
Am I suffering from acute caffeine deficiency syndrome \(just made it
up\) or is there a problem with the occurrences of event and
interval\_events in the blood pressure archetype?
In the published blood pressure archetype in the CKM, HISTORY\[at0001\]
has events with cardinality \{1\.\.\*; unordered\}
However "EVENT\[at0006\] occurrences matches \{0\.\.\*\}" and
"INTERVAL\_EVENT\[at1042\] occurrences matches \{0\.\.1\}" under the history
allow zero instances of both of these elements\.
So the cardinality sets 1 as the minimum member count for the
container attribute, but occurrences attributes of objects introduce
0, which is beyond allowed boundaries\. In plain English: cardinality
says there has to be at least one, but objects say, there can be zero
or more\. When both objects have zero instances, the cardinality
constraint is violated\.

Comments?

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## Post #2 by @system

Hi Seref,

I am suffering from the same \+ the heat from possibly the first summer
day in Germany this year, but I think this is perfectly correct\.
As far as i understand, it just means you have to choose at least one
at0006 EVENT or one at1042 INTERVAL\_EVENT\.
Then you can add as many further at0006 events as required\.

So, you are right, they cannot both have zero instances, but you can
choose, and a cardinality of >=1 and member elements with occurrence >=
0 is the way to express this choice I believe\.

Sebastian

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## Post #3 by @Seref

Hi Sebastian,
If I follow the descriptions from the specification, I don't think I
can see anything in there that says you have to choose at least one in
this case\.
Actually page 56 of the adl 1\.4 specification \(
http://www.openehr.org/releases/1.0.1/architecture/am/adl.pdf \)
specifically says the following:

VCOC: cardinality/occurrences validity: the interval represented by:
\(the sum of all
occurrences minimum values\) \.\. \(the sum of all occurrences maximum values\) must
be inside the interval of the cardinality

If I were to write a validator based on this, it would invalidate the
blood pressure archetype based on the criteria above taken from the
spec\.

What you're saying makes sense, but I can't see it in the specification\.

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## Post #4 by @system

Hi Seref,

This means \- you have to have at least one event, but it could be either
EVENT or INTERVAL\_EVENT\.

Does that make sense\.

Cheers, Sam

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## Post #5 by @system

Hi Seref,

interesting, I think Thomas changed this rule for ADL 1.5 to:
VACMC - cardinality/occurrences validity: where occurrences and cardinality are stated, the interval represented by: (sum of all occurrences minimum values) .. (sum of all occurrences maximum values) must intersect with the interval stated by the cardinality.

Thomas and I had a discussion about some edge cases here a while ago, where you could make this rule a little more strict potentially, but in any case it seems to be a necessary condition for a correct archetype.

My take is that VCOC prevents functionality that is needed and is simply too strict and was therefore modified to VACMC in ADL1.5 - Thomas?

Sebastian


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## Post #6 by @thomas.beale

Yes. We should allow the two 0..x constraints. The cardinality constraint says you must have at least 1 thing in the list, and the two other constraints each say - separately - that the EVENT and INTERVAL_EVENT matching objects can single have 0 instances. Taken together, it is all compatible. The reworded rule above, quoted by Sebastian, says that it has to be at least *possible* to meet the constraints.

- t

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## Post #7 by @Seref

Thanks Tom,
The reworded rule is what I was asking for actually: something in the
spec that sets the rule for this particular combination of values\.

Cheers
Seref

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**Original content:** https://discourse.openehr.org/t/question-about-occurrences-and-cardinality-values-in-the-blood-pressure-archetype/15081