This migration task has to:
Get all nodes from data workspace that have a property with a certain name
This property may contain a dms UUID.
The task has to check if this document is present in DAM workspace.
If this is the case, the UUID is transformed into a DAM composite ID.

http://wiki.magnolia-cms.com/display/DEV/Concept+-+Migration+from+DMS+to+DAM#Concept-MigrationfromDMStoDAM-UpdateDataNodespropertiesfromDMSDatatoDAMreferences