This functionality is needed for ability to calculate automatically total amount of related documents.

You should specify such beanL
<bean id="nameYouurBean" parent="idocs.totalDocumentsSumBehaviour">
<property name="className" value="forDocumentsThisType"/>
<property name="assocName" value="relatedThisAssoc"/>
<property name="sumField" value="fromThisDocumentAmount"/>
<property name="totalSumField" value="toThisTotalAmount"/>
</bean>

All properties are QName. Total amount is calculated from all targets in order to source recursively