Product/Kit dimension and fact table question

[Database Administrator]

This seems like it should be fairly simple, but I think I may be too close
to the situation and missing something obvious.

I have a situation where the fact table will contain line item detail from
sales orders so each fact will contain a quantity and extended price value
for a given item# on a sales order.

The complication comes in knowing how to factor in the "kitting" which takes
place. For Kit #ABC includes part numbers #111, #222, #333 and #444. When
the kit is sold, all four of those parts will appear in the fact table as
separate rows with a Quantity of 1. Those same items can be sold on their
own (apart from the kit), in which case another row in the table might exist
for part number #111 with a Quantity of 1.

Getting a sum of the number #111 sold works well, but what if I want to get
a sum of the number of kit #ABC sold? Anything I do at the dimension end
still seems to result in over counting since the quantity is at the
individual item level (i.e. components of the kit).

One thought I've had is to have a ItemQuantity field and a separate
KitQuantity field. The ItemQuantity field would be treated the same as
described above. The KitQuantity field would act much like an allocation
whereby the quantity of the kit ordered would be distrubuted among the kit
components. In the example above, the KitQuantity would be 0.25 for each of
the 4 items making up the kit. Extended price would be handled in a simliar
fashion.


Does this approach make sense, or is there a better, more standard approach
for dealing with the heirarchy of items/kits while maintaining the
intregrity of the quantity and extended price fields?

Thanks!

Steve