Lecture Accounting information systems: Chapter 3 - Richardson, Chang, Smith

Chapter 3 - Data modeling. After reading this chapter, you should be able to: Understand the purpose of structure models, understand and apply the building blocks for UML class (structure) diagrams, describe multiplicities for a UML class diagram, understand how to implement a relational database from a UML class diagram, describe business rules and the various forms of rules.

Chapter 3

Data Modeling

Copyright © 2014 McGraw­Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw­Hill Education.

Learning Objectives

• LO#1 Understand the purpose of structure models.

• LO#2 Understand and apply the building blocks for UML

Class (structure) Diagrams.

• LO#3 Describe multiplicities for a UML Class Diagram.

• LO#4 Understand how to implement a relational

database from a UML Class Diagram.

• LO#5 Describe business rules and various forms of

rules.

Structure Models

structures inherent in a business process

a relational database to support the

collection, aggregation, and

communication of process information

are implemented

3-3

Unified Modeling Language (UML)

models

Object Management Group, a not-for-profit consortium of computer industry members

other types of diagrams, including several

structure diagrams, behavior diagrams,

and interaction diagrams

structure of a database system

3-4

UML Class Diagram – Building Blocks

collections of things about which the

organization wants to collect and store

information

between two classes

maximum number of times instances of

one class can be associated with

UML Class Diagram - Classes

– organization resources (e.g., trucks, machines, buildings,

cash, investments)

– events (e.g., sales, purchases, cash disbursements, cash

receipts), and conceptual structures (e.g., accounts, product categories, budgets)

UML Class Diagram - Associations

two classes

3-7

UML Class Diagram - Multiplicities

Each Person owns a minimum of 0 and a maximum of many

Autos Each Auto is owned by a minimum of 1 and a maximum

of 1 Person

number of times instances in one class can be

associated with instances in another class

Example of Association with Multiplicities Options for Multiplicities

Person 1 1 owns 0 * Auto

Multiplicities (Cardinalities)

Indicator Meaning 0 1 Zero or one 1 1 One only 0 * 0 or more 1 * 1 or more

the characteristics of instances in a class

(or rows in a table)

data dictionary, would also include data

type, default value (if any), constraints on

the value (such as minimum and

maximum possible values), and other

descriptive information

uniquely define instances of the class,

foreign keys that support the links

between classes shown in the

associations, and other data elements for

each class

that accompanies each class diagram

3-9

Primary Keys

that uniquely identifies each instance in a

class or row in a table

organization that assigns it so it will not

change over time

Foreign Keys

3-11

tables to be linked together

tables) shown by the associations

class would become a foreign key in the AUTO class to

implement the association

Table Listing - Example

Customers [Customer_Number (PK), Customer_Name, Customer_City, Customer_State,

Customer_Zip, Customer_Phone]

Orders [Order_Number (PK), Order_Date, Delivery_Date, Order_Amount, Shipping_Cost,

Customer_Number (FK)]

Order_Items [Order_Number + Product_Number (PK), Quantity_Ordered, Price]

Inventory [Product_Number (PK), Product_Description, Quantity_on_Hand (QOH), Unit_of_Issue,

Current_List_Price, Standard_Cost]

Best Practices in Preparing Class Diagrams

organization for class names

there is a clear business purpose for the

relationship

together

then address appearance

situations

3-13

Implementing a Database from a Class

Diagram

assign primary keys

many-to-many relationships

following the class diagram

1 Map Classes to Tables

3-15

2 Map Class Attributes to Table Fields and

Assign Primary Keys

3 Map one-to-many associations to foreign

keys

3-17

One-to-many associations are defined by the maximum multiplicity on

each end of the association The rule of thumb is to go toward the * to

post the foreign key So, in the model above, the primary key of

STATE would be a foreign key in AUTO; the primary key of PERSON

would be also be a foreign key in AUTO See Table 1 in Chapter 3 for

a listing of posting rules based on multiplicities

4 Create New Tables to Implement

Many-to-Many Relationships

Many-to-many associations require the creation of a new, linking table

to implement the association So, in the model above, the association

between DEALERS and AUTO would be implemented with a new

table DEALER-AUTO with a primary key formed as the combination of

primary keys from the two classes.

5 Implement Relationships Among Tables

3-19

Business Rules

business process

however, they influence the structure and

flow of models

set criteria for branching in activity models

standards for Semantics of Business

Vocabulary and Business Rules (SBVR)

since 2008

since they limit the number of options

allowed by business policy

3-20

Types of Business Rules

should occur: payment should be made in

U S dollars

should not occur: no payments by check

allowed under what conditions: credit card payments are allowed if the card is

American Express

3-21