The <Parent_SERF> field allows the capability to relate generalized aggregated metadata records (parents) to metadata records with highly specific information (children). Population of the <Parent_SERF> field should be reserved for instances where many metadata records are basically subsets that can be better represented by one parent metadata record, which describes the entire collection. Typically, the parent metadata record will have many children metadata records, which refer to the parent through the <Parent_SERF> field. In some instances, a child may point to more than one parent. The <Parent_SERF> is populated with an <Entry_ID>. 

The <Parent_SERF> is only populated if there are children metadata records that refer to a parent metadata record.  Upon display of results, both parent and children metadata are available with explicit linkages between parent and child records through the <Parent_SERF> field.