OWB Newbie - Joining Dimensions to Fact Tables

Question

Hello Forum,
This may seem like a simple question, but the documentation is so lacking that I can't seem to find the answer to "how does the tool" work.
I am creating a simple data mart starting with a star schema and choosing a deployment option of ROLAP.
When using the OWB Tool to create dimensions and fact tables, do you need to define your primary business key (coming from your source system) in each fact table for each dimension that will join to that fact table? I am assuming yes, at least at the lowest leaf level of the dimension hierarchy in this case Store_ID. How else would you be able to correctly join a particular sales order record to the store that it was sold in? a simple query that we know our users will execute for reporting purposes. To make myself clear here is a simple example:
Dimension = Store
Hierarchy = Store ----> Sales Territory ---->Region ----->Country
Attributes = Store ID (primary business key), Store_Name, Sales_Territory_ID, Sales_Territory_Description, Store_Manager_Name, Store_Location etc.,
Cube or Fact Table = Sales Orders
Measures = sale_price, quantity, drop_ship_cost, sales_tax, etc.,
Do I also need to create an attribute for Store ID so that when I load each sales order record into the fact table along with it comes it's proper Store ID?
I understand how the tool uses the surrogate key and business identifier to create a foreign key look-up from dimension to fact table and pull in the correct store description (i.e. name) but unless you have the Store ID as part of the sales record being loaded into the fact table I don't see how the you can traverse the table and join a sales order to it's proper store?
Can someone who is farther along in the process or has more experience with other components of the tool confirm my assumption or set me straight on how the tool accomplishes this?
thanks
monalisa

Answer 1

Hi Monalisa, I'll reply assuming your using OWB 10gR2.
First off, for each of the dimensions, you'll define a business key (as you noted below). Then, when you define the cube object, you'll tell it which dimensions you are using, along with the measures you will be storing.
When you drop a "cube" object into a map, it will show the measures, but it will replace the dimensions with their natural keys. I.e. in your example below, if your sales order cube had ONLY the store dimension, then the cube object will show up in a mapping with the measures of sales_price, quantity, drop_ship_cost, etc., but instead of showing the dimension for store, it will instead show the natural key Store_ID. When you map your data to load (which should be by store_id), OWB will automagically look up the proper dimension keys and do everything else for you.
Hope this helps!
Scott