Directory UMM :Slide_Kuliah:PPT:SIM_McLeod_8:
MANAGEMENT INFORMATION SYSTEMS 8/E
Raymond McLeod, Jr. and George Schell
Appendix A
Data Modeling
Copyright 2001 Prentice-Hall, Inc.
A-1
Data and Process Modeling
During systems development both processes
and data must be modeled
– Data modeling describes data used by system
– Process modeling describes processes carried out
by system
Level of detail
– Varies between highest summary and lowest detail
– Structured tools enable level of detail to be varied
A-2
Entity-Relationship
Diagram (ERD)
Documents firm’s data by identifying types
of data entities and their interrelationships
Prepared at “big picture” point of data
specification
Very flexible
A-3
Entity Types
Environmental
Resource
Important transaction
Entity
symbol
A-4
Relationship
An association between two entity types
Relationship
symbol
Employee
Fills out
Time card
A-5
Number of times an entity occurs
in relation to another entity
Connectivity
Time card
1
Produces
1
Payroll
check
M
Inventory
item
A. One to one
Invoice
1
Contains
B. One to many
Customer
M
Purchases
M
Product
C. Many to many
A-6
Attributes
Characteristics of an entity
Actually data elements
Identifiers are unique attributes of the entity
Descriptors describe the entity
A-7
Preparation of an EntityRelationship Diagram
1. Identify the entities
2. Identify the relationships
3. Prepare a rough ERD
4. Map data elements to the entities
5. Perform a data analysis (through third normal
form is common)
6. Prepare a modified ERD
7. Review the ERD with users and refine
A-8
Rough ERD
Supplier
Supplier number
1
Fills
M
Purchase
order number
Purchase
order
M
Contains
M
Raw
Material
M
Represents
Item number
1
Supplier number
Accounts
payable
A-9
Normalization
First normal form (1NF)
– Eliminate repeating elements in an entity
Second normal form (2NF)
– Ensure that descriptor attributes rely on the entire
composite key for the assignment of values
Third normal form (3NF)
– Ensure that an attribute value cannot be
determined by values of other attributes
A-10
Supplier number
Supplier name
Supplier address
Supplier
1
Purchase order number
Purchase order date
Fills
Supplier number
Supplier name
M
Supplier address
Item number (n times)
Purchase
Item description (n times)
order
Item quantity (n times)
Item unit price (n times)
M
Item extended price (n time)
Purchase order amount
Represents
Supplier number
Supplier name
Supplier address
Total accounts payable
1
Accounts
payable
Data Elements
are Mapped
M
Contains
M
Raw
Material
Item number
Item description
Warehouse location
Item unit price
Balance on hand
Reorder point
Order quantity
Quantity on hand
A-11
Normalized Portion of ERD
PURCHASE
ORDER
1
M
CONTAINS
PURCHASE ORDER
NUMBER
Purchase order date
Supplier number
Supplier
Supplier address
Purchase order amount
PURCHASE
ORDER
LINE
1
1
REPRESENTS
PURCHASE ORDER NUMBER
ITEM NUMBER
Item number
Item description
Item quantity ordered
Item unit price
Item extended price
RAW
MATERIAL
LINE/ITEM NUMBER
Item description
Warehouse
location
Item unit price
Balance on hand
Recorder point
Order quantity
Quantity on order
A-12
Data Dictionary
Written description of the data contained in
the database
First ones maintained in hardcopy form
Most are now maintained on a computer
Data flow dictionary entry describes data
flows on DFD
A-13
Data Dictionary [cont.]
Data store dictionary entry describes unique
data stored in a DFD
Data structure dictionary entry is completed
for each structure listed on the data store and
data flow forms
Data element dictionary entry is used for
each data element, or attribute included in all
of the structures
A-14
Data Flow Dictionary Entry
Data flow name:
Sales Order
Description:
The documents that are filled
out by customers to identify
the products, and the
quantities of each, that they
will wish to purchase.
From:
1. Open mail
To:
information
2. Enter sales order
Data structures:
Sales order record
Comments:
A-15
Data Store Dictionary Entry
Data store name:
Sales order form
Description:
The history file of sales order forms, after
the data has been entered into the sales
commission system.
Data structures:
Sales order record
Volume:
Approximately 140 per day
Activity:
Access:
Order department personnel
Comments:
A-16
Data Structure Dictionary Entry
Structure name:Sales order record
Description:
The sales order form that the customer uses to
order merchandise.
Date elements: Customer.Number
Customer.Order.Number
Salesperson.Number
Customer.Order.Date
*Item.Number
*Item.Description
*Item.Quantity
*Item.Unit.Price
*Item.Extended.Price
Comments:
Elements marked with asterisks occur for each
item record
A-17
Data Element Dictionary Entry
Data element name:
Salesperson.Number
Description:
The number that identifies the salesperson
Type:
Numeric
Length:
4
No. decimal pos.
Aliases:
Salesman number, Sales rep number
Range of values:
0001-9999
Typical value:
Specific values:
Other editing details:
A-18
Summary
During early years of computing, emphasis
was on the processes performed.
Currently, emphasis is on data
ERDs are a primary tool in data analysis
Data dictionaries provide a means of
documenting data
A-19
Raymond McLeod, Jr. and George Schell
Appendix A
Data Modeling
Copyright 2001 Prentice-Hall, Inc.
A-1
Data and Process Modeling
During systems development both processes
and data must be modeled
– Data modeling describes data used by system
– Process modeling describes processes carried out
by system
Level of detail
– Varies between highest summary and lowest detail
– Structured tools enable level of detail to be varied
A-2
Entity-Relationship
Diagram (ERD)
Documents firm’s data by identifying types
of data entities and their interrelationships
Prepared at “big picture” point of data
specification
Very flexible
A-3
Entity Types
Environmental
Resource
Important transaction
Entity
symbol
A-4
Relationship
An association between two entity types
Relationship
symbol
Employee
Fills out
Time card
A-5
Number of times an entity occurs
in relation to another entity
Connectivity
Time card
1
Produces
1
Payroll
check
M
Inventory
item
A. One to one
Invoice
1
Contains
B. One to many
Customer
M
Purchases
M
Product
C. Many to many
A-6
Attributes
Characteristics of an entity
Actually data elements
Identifiers are unique attributes of the entity
Descriptors describe the entity
A-7
Preparation of an EntityRelationship Diagram
1. Identify the entities
2. Identify the relationships
3. Prepare a rough ERD
4. Map data elements to the entities
5. Perform a data analysis (through third normal
form is common)
6. Prepare a modified ERD
7. Review the ERD with users and refine
A-8
Rough ERD
Supplier
Supplier number
1
Fills
M
Purchase
order number
Purchase
order
M
Contains
M
Raw
Material
M
Represents
Item number
1
Supplier number
Accounts
payable
A-9
Normalization
First normal form (1NF)
– Eliminate repeating elements in an entity
Second normal form (2NF)
– Ensure that descriptor attributes rely on the entire
composite key for the assignment of values
Third normal form (3NF)
– Ensure that an attribute value cannot be
determined by values of other attributes
A-10
Supplier number
Supplier name
Supplier address
Supplier
1
Purchase order number
Purchase order date
Fills
Supplier number
Supplier name
M
Supplier address
Item number (n times)
Purchase
Item description (n times)
order
Item quantity (n times)
Item unit price (n times)
M
Item extended price (n time)
Purchase order amount
Represents
Supplier number
Supplier name
Supplier address
Total accounts payable
1
Accounts
payable
Data Elements
are Mapped
M
Contains
M
Raw
Material
Item number
Item description
Warehouse location
Item unit price
Balance on hand
Reorder point
Order quantity
Quantity on hand
A-11
Normalized Portion of ERD
PURCHASE
ORDER
1
M
CONTAINS
PURCHASE ORDER
NUMBER
Purchase order date
Supplier number
Supplier
Supplier address
Purchase order amount
PURCHASE
ORDER
LINE
1
1
REPRESENTS
PURCHASE ORDER NUMBER
ITEM NUMBER
Item number
Item description
Item quantity ordered
Item unit price
Item extended price
RAW
MATERIAL
LINE/ITEM NUMBER
Item description
Warehouse
location
Item unit price
Balance on hand
Recorder point
Order quantity
Quantity on order
A-12
Data Dictionary
Written description of the data contained in
the database
First ones maintained in hardcopy form
Most are now maintained on a computer
Data flow dictionary entry describes data
flows on DFD
A-13
Data Dictionary [cont.]
Data store dictionary entry describes unique
data stored in a DFD
Data structure dictionary entry is completed
for each structure listed on the data store and
data flow forms
Data element dictionary entry is used for
each data element, or attribute included in all
of the structures
A-14
Data Flow Dictionary Entry
Data flow name:
Sales Order
Description:
The documents that are filled
out by customers to identify
the products, and the
quantities of each, that they
will wish to purchase.
From:
1. Open mail
To:
information
2. Enter sales order
Data structures:
Sales order record
Comments:
A-15
Data Store Dictionary Entry
Data store name:
Sales order form
Description:
The history file of sales order forms, after
the data has been entered into the sales
commission system.
Data structures:
Sales order record
Volume:
Approximately 140 per day
Activity:
Access:
Order department personnel
Comments:
A-16
Data Structure Dictionary Entry
Structure name:Sales order record
Description:
The sales order form that the customer uses to
order merchandise.
Date elements: Customer.Number
Customer.Order.Number
Salesperson.Number
Customer.Order.Date
*Item.Number
*Item.Description
*Item.Quantity
*Item.Unit.Price
*Item.Extended.Price
Comments:
Elements marked with asterisks occur for each
item record
A-17
Data Element Dictionary Entry
Data element name:
Salesperson.Number
Description:
The number that identifies the salesperson
Type:
Numeric
Length:
4
No. decimal pos.
Aliases:
Salesman number, Sales rep number
Range of values:
0001-9999
Typical value:
Specific values:
Other editing details:
A-18
Summary
During early years of computing, emphasis
was on the processes performed.
Currently, emphasis is on data
ERDs are a primary tool in data analysis
Data dictionaries provide a means of
documenting data
A-19