Selecting R'EPOSITORIES'






Selecting REPOSITORIES

There are five ENTITIES in the design that are roots of AGGREGATES, so we can limit our consideration to these, since none of the other objects is allowed to have REPOSITORIES.

To decide which of these candidates should actually have a REPOSITORY, we must go back to the application requirements. In order to take a booking through the Booking Application, the user needs to select the Customer(s) playing the various roles (shipper, receiver, and so on). So we need a Customer Repository. We also need to find a Location to specify as the destination for the Cargo, so we create a Location Repository.

The Activity Logging Application needs to allow the user to look up the Carrier Movement that a Cargo is being loaded onto, so we need a Carrier Movement Repository. This user must also tell the system which Cargo has been loaded, so we need a Cargo Repository.

Figure. REPOSITORIES give access to selected AGGREGATE roots.

graphics/07fig04.gif

For now there is no Handling Event Repository, because we decided to implement the association with Delivery History as a collection in the first iteration, and we have no application requirement to find out what has been loaded onto a Carrier Movement. Either of these reasons could change; if they did, then we would add a REPOSITORY.


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