Hi Sam, Thanks for your (always) kind answer...My comments & reply is below
Sam Heard wrote: > Hi Kory > > You can have an empty cluster....if you want to say why it is empty > then use null flavor on one or more of the possible elements. Yes this is exactly what can be done now...But when starting to think (or even implement) archetypes not merely as abstract clinical concept models but as objects or program data (as instances) then this may issue become more obvious. > > If these do not suffice as approaches I probably need the precise > example. It suggests that your model may not be optimal. > > Cheers, Sam Well you are definitely right (and polite) about my models...I also suspect that they are might not only be optimal but I am trying. The previous example was meant to be the precise example but I assume did not make sense (even to me now!). Well instead of an example I will shortly summarize the issue by example: Consider instances of some archetype; let's say with 2,3 levels of nested Clusters each having many elements in leaf nodes. The archetype may describe a cardiovascular patient history and these particular clusters happen to define Risk factors. So one path might be: > Risk factors > Smoking > Cigarette > Quantity. And if a patient has no risk factors, all the entries will be null in runtime instance and eventually in the database. Think about the simplicity of putting a flag or null_flavor at the top node so that a query or a GUI generator will utilize for better performance. Is there any other way than checking each path for element value/null_flavor path? And think about this for millions of records. What disturbs me most with as is approach is that the control is transferred to implementors in deciding to either put an element under each cluster or depict presence/null_flavor on clusters. Thanks for your patience... -koray _______________________________________________ openEHR-technical mailing list openEHR-technical at openehr.org http://www.chime.ucl.ac.uk/mailman/listinfo/openehr-technical
