The following rule applies for cross deployment access:
You cannot use a cross-deployment-unit association to access a business object in another deployment unit. You can only use a cross-deployment-unit association in an analytical data source to collect data from a business object residing in a different deployment unit.
Business objects in the Foundation deployment unit cannot access any business object residing in another deployment unit.
You can read the data of cross deployment business object by using a Query, Retrieve method or an Association