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The SourceOID references the source (start) structural element of the transition. This can e.g. be a StudyEventGroup, a StudyEvent, and ItemGroup, or an Item.
The TargetOID references the target (end) structural element of the transition. This can e.g. be a StudyEventGroup, a StudyEvent, and ItemGroup, or an Item.
The StartConditionOID references a ConditionDef defining the condition under which the transition can be started. When the source structural element can be considered to be a "visit", the condition can be regarded as a visit exit criterion.
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