RE: How-to implement the e-Commerce-System found in the "IDDD" book

I would create 3 IntelliJ projects products, orders and invoices.

An order would be only associated with a product by a simple product-ID.

An invoice would only know about its order by means of a order-ID.

[.m] not really, you need to de-normalize in the order and in the invoice the basic info of the "related" item, for 2 reasons:

-          History: invoices and orders cannot change once emitted, so I f the product description changes the description on the invoice should not change;

-          Independency: Order-BC should not depend on the availability of the Product-BC to work;



Let me just go through two usecases:



Use-case "Deleting an Order."



With the first implementation this is very easy.

I just need to call the order's delete method which also just deletes its contained invoices.



With the second implementation I probably need some kind of event-system so that the invoice subdomain can react on a  Order-Delete Event.

[.m] yes, I agree



Use-case "Reporting of all invoices grouped by a catalog item"



In the first implementation I would find all products of an catalog and then find the  associated  orders.

I would  then just iterate over the invoices to produce the report.



In the second implementation I would do basicly the same steps. But since I'll have to deal with three systems the "services" have to do internally a lot of lookups based on product and order IDs. So I do expect to performance-wise to need to tune here a lot.

[.m] or you have a fourth BC, the stats one, that reacts to all events in the system and creates the stats data ready for managers queries.



.m