I am trying to create/add to our Inventory relation by allowing the database
to store information on discounts. I want to be able to define rules that
would apply to Inventory.

I have one component complete, that being the ability to define specials
such as all Inventory within a ProductLine between StartDate and EndDate
will be 20% off.
That looks like this:
Table Name = LineDiscount
Attributes are:
StartDate
EndDate
DiscPct
StoreId
InventoryId
CategoryId
ProductLineId
MfrId
VendorId

I want to also be able to apply rules such as the following
Buy x get y free
Buy qty x get x for $
Buy x and y get % off

I think these are similar to the more sophisticated modeling being done, but
I am struggling with how to best design the database to store the "rules" so
my application can use them.

I am hoping someone has ideas and/or experience with this type of design and
can offer some examples or other resources to help me find the solution.

Thanks
WB