Entity Relationship Diagrams (ERDs)

Entity Relationship Diagram (ERD) documentation technique to represent relationship between entities in system. Think of entities as “nouns” – nouns on which a company would want to track information. A few examples: Vehicles Accounts Receivable Customers Vendors 2

Entity Relationship Diagram (ERD) Think of the relationship as a “verb” The verb connects (relates) one entity to another. A few examples: Receive Assign Prepare Send 3

4 Cardinality between entities represents the numerical mapping between entities: one-to-one one-to-many many-to-many Depends on business rules !!

Sales- person Car Customer is assigned EntityRelationshipEntity 1 1 Company A

Sales- person Car Customer is assigned EntityRelationshipEntity M1 Company B

7 Customer Order places EntityRelationshipEntity M 1 This cardinality is probably true for most businesses.

8 VendorInventory supplies EntityRelationshipEntity M M This cardinality would depend on the business.

ERD – Expenditure Cycle

10 Describe the business rules represented by the cardinalities in the ERD. P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1

11 Add 3 attributes for each entity. P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1

12 3 attributes for each entity. P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1

13 Modify the ERD, based on the following information: The Vendor sends an invoice for each shipment. The invoice is matched to the RR; a Cash Disbursement (CD) is prepared for each invoice. 13 P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1

14 P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1

15 P.O. REC. RPT. INVENTORY VENDOR M M 1 M 1 M M M 1 1 Add 3 attributes for each new entity.

16