design.txt

Relational Schema Design:
The relational schema consists of 4 relations. These are as follows:
1) bids(item_id, user_id, time, bid_amount)
2) auctionusers(user_id, rating,location,country)
3) items(item_id, name, currently, first_bid, number_of_bids, started, ends, seller_id, description, buy_price)
4) categories(item_id, category)

The schema is in 4NF. The steps from the mega-relation to the current relations is as follows:
1) Mega-relation(item_id, name, currently, first_bid, number_of_bids, started, ends, seller_id, seller_rating, seller_location, seller_country, description, buy_price, user_id,user_rating, time, bid_amount, category)
MVDs:
item_id -->>(category)
user_id -> (rating, location, country)
seller_id follows the same MVD as user_id (and refers to the same data)
item_id -->>(user_id,time, bid_amount)

2) Splitting the relations to ensure that the keys remain on the left of the dependencies listed above.

Categories = R1(item_id, category),
Auctionusers = R2(user_id, rating,location,country)
Bids = R3(item_id,user_id,time,bid_amount)
Items = R4(item_id, name, currently, first_bid, number_of_bids, started, ends, seller_id, description, buy_price)