1. PEMODELAN SISTEM
Process Modeling
Data Modeling

2. 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

3. Process Modelling
Copyright 2001 Prentice-Hall, Inc. 1

4. Data Flow Diagrams (DFDs)
Graphic representation of a system that uses a small number of symbol shapes to illustrate how data flows through interconnected processes
Most natural way to document processes
Emphasis on processes rather than data
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5. DFD Symbols DFDs consist of four symbols
1) Environmental elements called terminators
Person
Organization
Another system
2) Processes which transform inputs to outputs
Labeled with verb and object
Also labeled with system or computer program name
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6. DFD Symbols [cont.] DFD symbols [cont.]
Data flows which consist of logically related data elements that travel from one point or process to another. In other words, data in motion.
Structures
Diverge
Converge
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7. DFD Symbols [cont.] DFD symbols [cont.]
Data stores which are data repositories. In other words, data at rest.
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8. A Data Flow Diagram (Figure 0 Diagram) of a Sales Commission System
Mail
A Data Flow Diagram (Figure 0
Diagram) of a Sales Commission
System
Customer 1.
Open
mail
Sales
orders
Entered
sales orders 2.
Enter sales
order data
Sales order
form file
Entered
sales order
data 3.
Sort
sales
order s
Sorted
sales
records
Sales commission
report
Sales
manager 4.
Compute
sales
commissions
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9. When Drawing a Context Diagram
1. Use only a single process symbol
2. Label the process symbol to represent the entire system
3. Do not number the single process symbol
4. Include all terminators for the system
5. Show all the data flows between the terminators and the system
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10. Sales Commission System
A Context Diagram of a
Sales Commission System
Customer
Mail
Sales
Commission
System
Sales
commission
report
Sales
Manager
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11. Figure n Diagrams
Documents a single process of a DFD in a greater amount of detail
n represents the number of the process on the next higher level that is being documented
The term “leveled DFDs” describe the hierarchy of diagrams ranging from context to the lowest-level figure n diagram
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12. Figure 4 Diagram of a Sales Commission System
Sorted
sales
records 3
4.1
Compute
commission
amounts
Sales
commission
report
4.2
Accumulate
totals
Sales
manager
Commission
amounts
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13. How Many Levels to Use?
Restrict a single DFD to no more than six to eight processes
Use another tool to document the lowest level of detail but use no more than a single page.
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14. Data Flow Diagramming Guidelines
1. Label each data flow with a unique name.
2. Keep data flow names constant between levels.
3. Show proper disposition of records deleted from a data store.
4. When documenting a computer program, do not include reads/writes.
5. Avoid read-only processes.
6. Write-only processes are permissible when time serves as the trigger.
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15. Structured English Narrative form of computer code documentation
Based on Pseudocode
Abbreviated, formalized pseudocode in a particular format that looks like computer code
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16. Structured English Guidelines
1) Use a verb when describing each processing strip.
2) Supplement verb with one or more objects when necessary.
3) Use only three constructs of programming.
Sequence
Selection
Repetition
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17. Structured English Guidelines [cont.]
4) Use only data names defined in the data dictionary.
5) Use uppercase for all data names and computer syntax.
6) Indent to show a hierarchical structure.
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18. Structured English Guidelines [cont.]
7) When documentation is subdivided into modules, use the first line of each module for an identifying label and leave at least one blank line in-between.
8) Restrict each module to a single entry and exit point.
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19. Structure English Example
START
Initialize storage
TOTAL.SALES, TOT.COM = 0
Process sales data
DO WHILE (more records)
PERFORM READ DATA PERFORM PROCESS DATA
PERFORM PRINT DATA
END DO
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20. Summary Process modeling is an important part of system design
Various techniques exist for process modeling
DFDs
Structured English
Manager can use Structured English and DFDs to communicate system requirements
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21. Data Modelling
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Copyright 2001 Prentice-Hall, Inc. 1

22. 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
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23. Entity Types Environmental Resource Important transaction Entity
symbol
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24. An association between two entity types
Relationship
An association between two entity types
Relationship
symbol
Time card
Employee
Fills out
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25. Number of times an entity occurs in relation to another entity
Connectivity
Number of times an entity occurs in relation to another entity 1 1
Payroll
check
Time card
Produces
A. One to one 1 M
Mahasiswa
Sebagai dosen
wali
Dosen
B. One to many M M
Mahasiswa
Mengambil
Matakuliah
C. Many to many
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26. Attributes Characteristics of an entity Actually data elements
Identifiers are unique attributes of the entity
Descriptors describe the entity
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27. Preparation of an Entity-Relationship 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
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28. Rough ERD Supplier number 1 Fills M Purchase order number M M Raw
Material
Contains M
Represents
Item number 1
Accounts
payable
Supplier number
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29. Normalization First normal form (1NF) Second normal form (2NF)
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
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30. Data Elements are Mapped Supplier number Supplier name
Supplier address
Supplier
Data Elements
are Mapped 1
Purchase order number
Purchase order date
Supplier number
Supplier name
Supplier address
Item number (n times)
Item description (n times)
Item quantity (n times)
Item unit price (n times)
Item extended price (n time)
Purchase order amount
Fills M M M
Purchase
order
Raw
Material
Contains M
Item number
Item description
Warehouse location
Item unit price
Balance on hand
Reorder point
Order quantity
Quantity on hand
Represents
Supplier number
Supplier name
Supplier address
Total accounts payable 1
Accounts
payable
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31. Normalized Portion of ERD
PURCHASE
ORDER 1 M
PURCHASE
ORDER
LINE 1 1
RAW
MATERIAL
CONTAINS
REPRESENTS
PURCHASE ORDER NUMBER LINE/ITEM NUMBER
PURCHASE ORDER
NUMBER
Purchase order date
Supplier number
Supplier
Supplier address
Purchase order amount
ITEM NUMBER
Item description
Warehouse location
Item unit price
Balance on hand
Recorder point
Order quantity
Quantity on order
Item number
Item description
Item quantity ordered
Item unit price
Item extended price
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32. 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
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33. 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
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34. 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: 2. Enter sales order information
Data structures: Sales order record
Comments:
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35. 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:
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36. 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
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37. 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:
Typical value:
Specific values:
Other editing details:
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38. 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
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