# Transitions\_valid invariant of STATE class
**URL:** https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126
**Category:** Reference Implementation: Java (archive)
**Created:** [6 July 2006 15:22 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126 "2006-07-06T15:22:22Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@rong.chen](https://discourse.openehr.org/u/rong.chen)
#### Post date: [6 July 2006 15:22 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126/1 "2006-07-06T15:22:22Z")
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
---
### Author:  [@thomas.beale](https://discourse.openehr.org/u/thomas.beale)
#### Post date: [7 July 2006 17:23 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126/2 "2006-07-07T17:23:50Z")
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
---
### Author:  [@thomas.beale](https://discourse.openehr.org/u/thomas.beale)
#### Post date: [7 July 2006 17:28 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126/3 "2006-07-07T17:28:12Z")
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
---
### Author:  [@rong.chen](https://discourse.openehr.org/u/rong.chen)
#### Post date: [8 July 2006 22:31 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126/4 "2006-07-08T22:31:15Z")
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
---
### Author:  [@thomas.beale](https://discourse.openehr.org/u/thomas.beale)
#### Post date: [9 July 2006 09:38 UTC](https://discourse.openehr.org/t/transitions-valid-invariant-of-state-class/12126/5 "2006-07-09T09:38:58Z")
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