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The OrderNumber attribute provides an ordering on the ItemGroupDefs (within StudyEventDef or ItemGroupDef) for use whenever a list of ItemGroupDefs is presented to a user. They do not imply anything about event scheduling, time ordering, or data correctness. Order of execution is preferably defined in a workflow (element WorkflowDef) but when used without a workflow, may be used the define the order in which data entry forms are presented in an application UI.
The Mandatory flag indicates that the clinical data for an instance of the containing form, studyevent event or itemgroup would be incomplete without an instance of this type of itemgroup. ODM clinical data files that are incomplete in this sense may be considered incomplete for study review and analysis purposes.
If the CollectionExceptionConditionOID attribute is provided, it the ConditionDef it references a ConditionDef that describes the circumstances under which data for this ItemGroup should not be collected.
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