CHAPTER 18
IMPLEMENTING AN REA MODEL IN A RELATIONAL DATABASE
SUGGESTED ANSWERS TO DISCUSSION QUESTIONS
18.1 How would the process of generating a cash disbursements journal from the REA
data model presented in Figure 18-4 and Table 18-1 differ from the process for
creating a sales journal?
18.2 Why take the time to develop separate REA diagrams for each business cycle if the
ultimate objective is to combine them into one integrated enterprise-wide data
model? Why not just focus on the integrated model from the start?
18.3 Building separate tables for every relationship (1:1, 1:N, and M:N) does not violate
any of the rules for building a well-structured database. Why then do you think that
REA data modelers recommend building separate tables only for M:N relationships
and using foreign keys to implement 1:1 and 1:N relationships?
18.4 Assume that there exists a 1:1 relationship between the Receive Inventory and
Disburse Cash events. How does the manner in which the relationship between the
two events is implemented (i.e., in which table a foreign key is placed) affect the
process used to record payments made to suppliers?
table.
18.5 Refer to Figure 18-4 and Table 18-1. How would you determine the amount of cash
that Fred’s Train Shop has at any point in time?
18.6 Why does Figure 18-4 show only one cash disbursement entity if Fred’s Train Shop
uses a general operating checking account for purchases of inventory, supplies, and
operating expenses such as rent but also uses a separate checking account for
payroll?
REA models do not represent actual physical accounts but types of accounts. Thus, even
18.7 Examine Figure 18-4 and Table 18-1. Why do the Inventory, Customers, and
Suppliers tables all have an attribute that contains data about the balance at the
beginning of the current fiscal period?
SUGGESTED ANSWERS TO THE PROBLEMS
18.1 Refer to Problems 17.1 and 17.2 for information about the revenue and expenditure
cycle activities for Joe’s ice-cream shop in order to draw an integrated REA
diagram of both cycles.
18.2 Develop a set of tables to implement the integrated REA diagram you developed in
Problem 18.1 for Joe’s ice-cream shop in a relational database. Specify a primary
key for each table, and suggest at least one other attribute that should be included in
each table.
Table Primary key Other attributes foreign keys in italics
Employees Employee# Name, date hired, salary, position
16.3 Refer to Problems 17.3 and 17.4 for information about Sue’s Gallery’s revenue and
expenditure cycle activities in order to draw an integrated REA diagram of both
cycles.
16.4 Develop a set of tables to implement the integrated REA diagram you developed in
Problem 18.3 for Sue’s Gallery in a relational database. Specify a primary key for
each table, and suggest at least one other attribute that should be included in each
table.
Table Primary key Other attributes foreign keys in italics
Vendor Vendor# Name, address, phone, contact, account balance
Employees Employee# Name, date hired, salary, date of birth, position
Purchases Purchase Order# Date, employee#, vendor#
Note: The cost and sales price are attributes of the inventory table because each unique
item is only purchased once and sold once.
The following tables and attributes exist in a relational database:
Table Attributes
Vendor Vendor#, name, street address, city, state
Disbursed
Draw an REA diagram for this database. State any additional assumptions you need
to make about cardinalities.
The solution appears on the following page. Students should be able to suggest adding
the entities connected by dotted lines, even though they are not listed in the problem. Key
assumptions about cardinalities include the following:
18.6 Refer to Problems 17.8 and 17.9 for information about the revenue and expenditure
cycles for the Computer Warehouse and use that information to draw an integrated
REA diagram for both cycles.
18.7 Develop a set of tables to implement the integrated REA diagram you developed in
Problem 17.6 for the Computer Warehouse in a relational database. Specify a
primary key for each table, and suggest at least one other attribute that should be
included in each table.
Table Primary key Other attributes (foreign keys in italics)
Vendor Vendor# Name, address, phone, contact
Employees Employee# Name, date hired, salary, date of birth,
position
GLaccount#
Customers Customer# Name, address, beginning balance
Inventory-Inventor
y
Item#