Online Sales System
ER\EER Diagram
Problem Statement
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The (Online Sales System) that will be developed will enable people in KFUPM
community to sale their items.
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People who want to sale their items, will post their items in the notice boards. A sample advertisement would
contains the name of items, description, price expected or best price, or negotiable In KFUPM community,
there are people who are selling and buying the items within the campus. People, who want to sell their items,
post the advertisement on the notice boards. A sample ad would look contain the name of the person, his
location, phone number(s), and the items list. The item list consists of the name of item, description, price
expected or best price, or negotiable. Complete details of the items are listed, and under what category of item
it belongs.
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In case of fixed price, the interested people would buy the item and the status of the item will change to sold
and it will not be listed for other buyers.
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In case of negotiable price, the seller will keep updating the highest price till he meets his deadline.
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In case of auction, bids made by the buyers are listed out these are seen by other buyers. The bids name,
address, phone(s) are stored. It depends on the seller whom to choose.
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As soon as all the items in the list are sold, the list should be deleted. If some items are left unsold, then there
should be a deadline for each list, after the deadline is over, these items information is removed.
Actually this problem statement does not
contain enough information!
But
we did our best to analyze it
Extracted Entities
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Initially we have found the following entities
Seller
Buyer
Item
List
Category
Order
But this is just the beginning!
Person Entity (One for all)
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We assign entity (Person) to be the super entity of Seller
and Buyer with the following attributes
• But with these attributes of Person, Seller and Buyer will not
have their unique attributes.
• That means Seller and buyer have the same attributes, thus we
decided to cancel Seller and Buyer and to add two more
attributes to Person to distinguish between them
Entities (Check Point)
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-
The new entities after reduction are
Person
Item
List
Category
Order
But life does not stop here!
Items (It is the one)
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•
•
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Item not only did not generate any problems but also
held (Category) to be one of its attributes instead to be an independent entity.
But unfortunately nothing is perfect, entity (items) has different types as
mentioned in the problem statement.
Item could be (Fixed Price, Negotiable, or Auction)
The final shape is the following:
Entities (Check Point)
•
-
The new entities after reduction are
Person
Item
List
Order
Be patient!
List (Easy come easy go)
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In the problem statement the word list was mentioned to be
an essential part, but we “as engineers” thought that it is not important
to include list in the diagram (at least from our point of view).
So, list was eliminated.
Entities (Check Point)
•
-
The new entities after reduction are
Person
Item
Order
Keep work!
Orders (Make your life easy)
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Orders can be an independent entity, it also can be
derived from the diagram, so we do not need to create an independent entity
Entities (Check Point)
• The new entities after reduction are
- Person
- Item
Have a cup of tea!
The Final Diagram
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