# Transitions_valid invariant of STATE class

**Category:** [Reference Implementation: Java (archive)](https://discourse.openehr.org/c/reference-implementation-java-archive/154)
**Created:** 2006-07-06 15:22 UTC
**Views:** 9
**Replies:** 4
**URL:** https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126

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## Post #1 by @rong.chen

Hi Thomas,

I am implementing Date\_types\.basic package and trying to create a test
C\_DV\_STATE with the medication order sample on p11 of openEHR Archetype
Profile document, rev1\.0\.

What I found is it is not possible to create the last state 'COMPLETED'
if the invariant of STATE class "Transitions\_valid: transitions /= Void
and then not transitions\.is\_empty" is in place\. Since it is the end
state, there is no more transition for that state\. Should the invariant
be changed to "Transitions\_valid: transitions /= Void \*implies\* not
transitions\.is\_empty"? Or I misunderstood something??

Regards,
Rong

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## Post #2 by @thomas.beale

Rong Chen wrote:
> Hi Thomas,
>
> I am implementing Date\_types\.basic package and trying to create a test
> C\_DV\_STATE with the medication order sample on p11 of openEHR Archetype
> Profile document, rev1\.0\.
>
> What I found is it is not possible to create the last state 'COMPLETED'
> if the invariant of STATE class "Transitions\_valid: transitions /= Void
> and then not transitions\.is\_empty" is in place\. Since it is the end
> state, there is no more transition for that state\. Should the invariant
> be changed to "Transitions\_valid: transitions /= Void \*implies\* not
> transitions\.is\_empty"? Or I misunderstood something??
>  

yes \- that is what it should read\.\.\.\.thanks for the fix\.\.\.\.

\- thomas

---

## Post #3 by @thomas.beale

Rong Chen wrote:
> Hi Thomas,
>
> I am implementing Date\_types\.basic package and trying to create a test
> C\_DV\_STATE with the medication order sample on p11 of openEHR Archetype
> Profile document, rev1\.0\.
>
> What I found is it is not possible to create the last state 'COMPLETED'
> if the invariant of STATE class "Transitions\_valid: transitions /= Void
> and then not transitions\.is\_empty" is in place\. Since it is the end
> state, there is no more transition for that state\. Should the invariant
> be changed to "Transitions\_valid: transitions /= Void \*implies\* not
> transitions\.is\_empty"? Or I misunderstood something??
>

actually, a better model would be to have an abstract class STATE, and
two concrete classes: TERMINAL\_STATE and NON\_TERMINAL\_STATE\. Then the
model falls out cleanly\. Or we can remain with the current model and
change "transitions" to being 0\.\.\* and change the invariant to allow this\.

\- thomas

---

## Post #4 by @rong.chen

Thomas Beale wrote:
> Rong Chen wrote:
>  
>> Hi Thomas,
>>
>> I am implementing Date\_types\.basic package and trying to create a test
>> C\_DV\_STATE with the medication order sample on p11 of openEHR Archetype
>> Profile document, rev1\.0\.
>>
>> What I found is it is not possible to create the last state 'COMPLETED'
>> if the invariant of STATE class "Transitions\_valid: transitions /= Void
>> and then not transitions\.is\_empty" is in place\. Since it is the end
>> state, there is no more transition for that state\. Should the invariant
>> be changed to "Transitions\_valid: transitions /= Void \*implies\* not
>> transitions\.is\_empty"? Or I misunderstood something??
>>
>
> actually, a better model would be to have an abstract class STATE, and
> two concrete classes: TERMINAL\_STATE and NON\_TERMINAL\_STATE\. Then the
> model falls out cleanly\. Or we can remain with the current model and
> change "transitions" to being 0\.\.\* and change the invariant to allow this\.

The specification looks much better now\. Thanks for the quick update\!
There is a minor detail though, both classes inherit STATE now \(as shown
in the UML\), but it's not clear in the class description\.

Cheers,
Rong

---

## Post #5 by @thomas.beale

Rong Chen wrote:
>
> The specification looks much better now\. Thanks for the quick update\!
> There is a minor detail though, both classes inherit STATE now \(as shown
> in the UML\), but it's not clear in the class description\.
>  

thanks \- fixed

\- thomas

---


**Canonical:** https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126
**Original content:** https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126