My point is;
IF Interval event exists, then it has an attribute of type DV_DURATION. DV_DURATION has no ability to be Void. Therefore, IntervalEvent.width cannot be Void. While I made a reference to, HISTORY, really has no application to this issue. I only made a reference so that others can fined it easily. While there are several DV_DURATION types in the HISTORY class; my question is only about the DV_DURATION of the "width" attribute of the Interval Event. DV_DURATION **EXPLICITLY** says that it cannot return a Void. However, the width attribute of the IntervalEvent class says *explictly* that it is void when an IntervalEvent is instantaneous. Yet, DV_DURATION can ***NEVER*** be Void, it must always have a value. So in simplicity I guess; how can I create a class that cannot return an instance with a void but in some instances this data type is *expected* to be void? Cheers, Tim On Sat, 2007-11-17 at 00:34 +1100, Andrew Patterson wrote: > > Duration of 0 makes much more sense to me as a duration value of an > > instantaneous event. > > > > > Well, I certainly agree that an instantaneous event cannot be an > > > interval event. However, there is some confusion in (my mind at least) > > > using the various DV_DURATIONS in History. But the biggest issue I have > > > is in dealing with the fact that an Interval Event has one and only one > > > DV_DURATION. DV_DURATION can never be Void. It MUST return a valid ISO > > > Date_Time value. > > I'm not really understanding the problem - HISTORY has a set of > EVENT's (base class) - > where the event can either be a POINT_EVENT (instantaneous, > no 'width' attribute in the class definition at all! therefore meeting > the requirement that width > is void), or it can be an INTERVAL_EVENT (this class does have a width > attribute of > type DV_DURATION, yet semantically can't have a width of 0 duration). > > It is correct that Interval Event has one and only one DV_DURATION - > to represent > an instantaneous event one has to _not_ use the interval event class, > instead using > the point event class. > > Andrew > _______________________________________________ > openEHR-technical mailing list > openEHR-technical at openehr.org > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical -- Timothy Cook, MSc Health Informatics Research & Development Services http://timothywayne.cook.googlepages.com/home LinkedIn Profile:http://www.linkedin.com/in/timothywaynecook
