Biztalk Bam Question:

An activity relationship exists when an activity relates to one or more other activities. An example of this is having multiple Shipment activities related to a single Purchase Order activity, or one Shipment activity containing items from two Purchase Order activities.

To indicate that two activities are related, you need to know both names and have the corresponding ActivityIDs in memory in order to call AddRelatedActivity. This API creates the link between the corresponding activity records.