Entity Relationship Diagrams (ERDs)

2

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

3

Entity Relationship Diagram (ERD)

Think of the relationship as a “verb” The verb connects (relates) one entity

to another. A few examples:ReceiveAssignPrepareSend

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

Entity Relationship Entity

1 1

Cardinalities

Company A

Sales-person

Car

Customer

is assigned

Entity Relationship Entity

M1

Cardinalities

Company B

7

Customer Orderplaces

Entity Relationship Entity

M1

Cardinalities

This cardinality is probably true for most businesses.

8

Vendor Inventorysupplies

Entity Relationship Entity

M M

Cardinalities

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 tothe 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

The End