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A reference to an ItemGroupDef as it occurs within a specific StudyEventDef or ItemGroupDef. The list of ItemGroupRefs identifies the types of item groups that are allowed to occur within this type of studyevent or (nested) itemgoup. The ItemGroupRefs within a single StudyEventDef or ItemGroupDef must not have duplicate ItemGroupOID or OrderNumber attribute values.
The MethodOID references a MethodDef used to pre-populate items.
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. 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.
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