Introduction
Entity relationship (ER) diagrams are used to construct entity-interrelated cause-and-effect schemes to describe a process, which usually involves multiple parties. Such diagrams are convenient because they reflect the sequence of activities and describe all the stakeholders and operations involved in the process, creating a complex picture. The scope of this essay is to critically evaluate the ER diagram created by Nicolaou et al. (2005). Figure 1 is an excerpt from this paper and serves as the object of analysis. Thus, the essay explores, describes, and interprets the relationships between the entity categories.
Analysis of the ER Diagram
As shown in the Figure, the ER diagram includes four primary entities: Customer, Order, Order_Item, and Item. The sequence of relationships between entities can be used to describe this process. First, a Customer — for whom contact information has been collected and assigned a unique number — places an order request. Information about this requisition includes the assigned ID and details of time, comments, and status. The entity contains a secondary key that associates a specific order with a specific customer. This means that although a single customer can place multiple orders, a single order cannot be placed by multiple customers simultaneously.
Second, the Order information is passed on and forms the order composition, which includes descriptions of the specific contents: the item the customer wishes to purchase and its quantity. A secondary key is also used here to link the order and its composition. Third, the Order_Item passes the item, which contains the item’s specific characteristics, cost, and description. A secondary key associates the order composition with the commodity — only one commodity corresponds to each order composition. Furthermore, Order_Item serves as a binding bridge between the customer and the commodity, as it characterizes the main features and attributes of the order.
Conclusion
Hence, this ER diagram can be used for e-commerce marketplaces where order placement and processing are relevant. However, the diagram needs to include additional links to show how the ordered goods are delivered to the customer, how payment is made and controlled, and who processes the order. In other words, from the Figure, the system works automatically, processing information about the request, order composition, and product without the involvement of the sales manager. A short text, including numeric attributes and text values, represents each of the four entities in the diagram.
Reference
Nicolaou, A. I., Essex, P. A., Raghunathan, M., & Liu, L. (2005). E-Hermes: An XML tool for the classroom. Journal of Information Systems Education, 16(3), 351-368.