# single-valued and container cardinality

**Category:** [Technical (archive)](https://discourse.openehr.org/c/technical-archive/156)
**Created:** 2006-10-03 04:32 UTC
**Views:** 2
**Replies:** 1
**URL:** https://discourse.openehr.org/t/single-valued-and-container-cardinality/12500

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## Post #1 by @Andrew_Patterson

The ADL spec \(section 4\.3\.3\) says that

"with no cardinality, the meaning is that each child object
constraint of the attribute in question is a possible
alternative for the value\.\."

i\.e\. that this attribute is "single\-valued" and the
types are multiple alternatives\.

It then gives an example and says

"here, the cardinality of the value attribute is 1\.\.1
\(the default\), which the occurrence of both QUANTITY
constraints is optional\.\.\."

I just wanted to confirm that the selection between
single\-valued and multi\-valued is dependant on the
\_absence\_ of a cardinality definition, not on whether
the cardinality is 1\.\.1\. So for a single value attribute,
it is actually illegal to put the "cardinality matches \{1\.\.1\}"
in the archetype definition??

Andrew

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## Post #2 by @thomas.beale

Andrew Patterson wrote:
> The ADL spec \(section 4\.3\.3\) says that
>
> "with no cardinality, the meaning is that each child object
> constraint of the attribute in question is a possible
> alternative for the value\.\."
>
> i\.e\. that this attribute is "single\-valued" and the
> types are multiple alternatives\.
>
> It then gives an example and says
>
> "here, the cardinality of the value attribute is 1\.\.1
> \(the default\), which the occurrence of both QUANTITY
> constraints is optional\.\.\."
>
> I just wanted to confirm that the selection between
> single\-valued and multi\-valued is dependant on the
> \_absence\_ of a cardinality definition, not on whether
> the cardinality is 1\.\.1\. So for a single value attribute,
> it is actually illegal to put the "cardinality matches \{1\.\.1\}"
> in the archetype definition??
>  

yes that is correct\. To be correct, "cardinality" is a property of
multiply valued attributes, not of single\-valued ones\. UML and many OO
books make a mess of this, and don't differentiate or even properly
define the meanings of "cardinality", "multiplicity", "optional", \.\.\.\.etc

\- thomas

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**Canonical:** https://discourse.openehr.org/t/single-valued-and-container-cardinality/12500
**Original content:** https://discourse.openehr.org/t/single-valued-and-container-cardinality/12500