# null value of Element

**Category:** [Technical (archive)](https://discourse.openehr.org/c/technical-archive/156)
**Created:** 2011-03-10 15:41 UTC
**Views:** 11
**Replies:** 1
**URL:** https://discourse.openehr.org/t/null-value-of-element/12925

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## Post #1 by @system

Hi,

I have an archetype with following Element

ELEMENT\[at0033\] occurrences matches \{0\.\.1\} matches \{    \-\- Condition Status
    value matches \{
       DV\_TEXT matches \{\*\}
    \}
\}

I noticed that it is not possible te create an Element\-instance with
data\-value null, because my own Object\-validator validates against this
archetype and complains that in this case, value is a required attribute\.

Now I wonder, is that so? Maybe I should change my object\-validator?

Is it so that in an archetype\-snippet like this, value is a required
attribute? Or is it also possible to use the nullFlavor\-attribute
instead, in that case I need to change my Object Validator

Thanks for any advise

Bert

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## Post #2 by @Peter_Gummer1

Bert Verhees wrote:

> ELEMENT\[at0033\] occurrences matches \{0\.\.1\} matches \{    \-\- Condition
> Status
>    value matches \{
>       DV\_TEXT matches \{\*\}
>    \}
> \}
> \.\.\.
>
> Is it so that in an archetype\-snippet like this, value is a required
> attribute?

According to the openEHR data structures specification, ELEMENT\.value
is 0\.\.1\. It's optional, as long as a null flavour is supplied\.

Invariants:
Is\_null\_valid: is\_null = \(value = Void\)
Null\_flavour\_indicated: is\_null xor null\_flavour = Void

In other words, \(value = Void\) = not \(null\_flavour = Void\)\. The
ELEMENT must have either a value, or a null flavour, but not both\.

\- Peter Gummer

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**Canonical:** https://discourse.openehr.org/t/null-value-of-element/12925
**Original content:** https://discourse.openehr.org/t/null-value-of-element/12925