note

asset is a single asset item type
asset type is a asset classification class
asset location provides where they are located
asset items in location sets each item in the location
asset item is assigned to a user

asset item has purchase record
asset item belongs to a user from an assigned date and can be re-assigned to different user on a different date
asset item can be discarded (state change)
asset item can be returned to an asset inventory when not in use