How to edit Relationship properties to only use part of the CDM Identifier in LDM?

Question

I'm creating a conceptual data model for a simplified web store using Power Designer.

I'm having trouble specifying the relation between an Order and a Receipt. I would like a receipt to only have a part of the order's identifier in its primary key in the logical model (more specifically, only order_id). I am unable to achieve this by tweaking the relationship properties (see the screenshots bellow; the problematic relationship is marked with a green arrow).

Should I simply omit the relation in the conceptual model?

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Conceptual data model

Logical data model

EDIT

If perhaps it wasn't clear how I envisioned my tables…

User

username	password	mail	first_name	last_name	address
hacker123	greenGrass	[email protected]	David	Norton	West Shire 40, 1240 Neverland
musicman100	SuperPassword	[email protected]	John	Stewart	Strange Alley 50, 1250 Outer Space

Product

product_id	name	description	price_per_unit	unit_of_measure	supply
1	Tooth Brush 100	NULL	5.99	piece	200
2	Super Paste 200	For sparkling smiles	7.99	piece	50

Order

order_id	username	product_id	amount
50	hacker123	1	2
50	hacker123	2	1
51	musicman100	1	5

Receipt

receipt_id	order_id
12	50
13	51

EDIT #2

I just realised that I should probably break up Order into two tables! One to track which products are on a particular order, and another to track who placed the order.

Perhaps I could even split the Order table into 3 parts

Order(order_id, order_time)

ProductsPerOrder(order_id, product_id, amount)

OrdersPlaced(order_id, username)

Answer 1

You can edit the relationship in the logical model!

If you click on a relationship, a Relationship properties dialog appears. There's a tab called Joins. This is where you can specify which columns to refer to with the relationship.

Answer 2

You have a contradiction... One part says that Order is identified by User+Product+Order; the other says that Order has its own identifier order_id.

I guess the second one is correct, with the usual design that Order has an id.

And you need to change the relationships in the CDM, between Order, and User/Product, to uncheck the Dependent property. These links are just mandatory, not dependent (which would mean that Order is defined relatively to User+Product).

p.s. the same holds for Receipt, which has its own identifier.