In another thread (http://vcampus.osisoft.com/discussion_hall/development_with_osisoft_sdks/f/28/p/4190/22305.aspx#22305) I claimed that it is highly discouraged for an event frame's attributes to be something other than a null data reference. Certainly that statement has some small exceptions: formulas to quickly calculate something. But I thought having PI Points or other historical items on an event frame are discouraged. I thought for sure this was written down somewhere and tried to find something to back up my claim. I can't find it in writing anywhere but perhaps I am looking in the wrong places.
To me, if you have something historical, it doesn't belong on an event frame. Rather it should be on an element. I think of a single PI Value as a value for some point in time. Likewise I think of attribute values on an event frame as being a value for some vector or segment in time. If you do have a PI Point on an event frame, is it possible to get values outside the StartTime-EndTime of the frame?
I didn't think there was technically anything stopping someone from having a PI Point on an event frame. But is it a good or recommended design?