[OT] Inventory systems (private)

Hi All,

is there any whitepaper, document or website that can point me to how to
setup a inventory system?
I'm particulary interested how other people solve the problem of a unknown
number of attributes to a inventory item.

example:
BAL                <-- Inventory Item- Color      <- Attribute- Diameter   <- Attribute- Weight     <- Attribute

Car                <-- Inventory Item- Speed      <- Attribute- Size       <- Attribute- Weight     <- Attribute- Color
    <- Attribute
 

Computer                <-- Inventory Item- Brand           <- Attribute- Weight          <- Attribute- Windows/Linux
<-Attribute
 


I can ofcource add any number of columns to a table but for a lot of items
there will be a lot of NULL values and currently I don't know how many
attrubutes one item can have (possible between 10 and 20). This can even
change in feature opon request.

Ries