Directory UMM :Slide_Kuliah:PPT:SIM_McLeod_8:
Appendix B
Process Modeling
MANAGEMENT INFORMATION SYSTEMS 8/E Raymond McLeod, Jr. and George Schell
(2)
Data Flow Diagrams
Data Flow Diagrams
(DFDs)
(DFDs)
Graphic representation of a system that uses Graphic representation of a system that uses
a small number of symbol shapes to a small number of symbol shapes to
illustrate how data flows through illustrate how data flows through
interconnected processes interconnected processes
– Most natural way to document processesMost natural way to document processes – Emphasis on processes rather than dataEmphasis on processes rather than data
(3)
DFD Symbols
DFD Symbols
DFDs consist of four symbolsDFDs consist of four symbols
1) Environmental elements called
1) Environmental elements called terminatorsterminators » PersonPerson
» OrganizationOrganization » Another systemAnother system
2)
2) ProcessesProcesses which transform inputs to outputs which transform inputs to outputs
» Labeled with verb and objectLabeled with verb and object
(4)
DFD Symbols [cont.]
DFD Symbols [cont.]
DFD symbols [cont.]DFD symbols [cont.]– Data flowsData flows which consist of logically related which consist of logically related data elements that travel from one point or
data elements that travel from one point or
process to another. In other words, data in
process to another. In other words, data in
motion.
motion.
» StructuresStructures » DivergeDiverge » ConvergeConverge
(5)
DFD Symbols [cont.]
DFD Symbols [cont.]
DFD symbols [cont.]DFD symbols [cont.]– Data storesData stores which are data repositories. In which are data repositories. In other words, data at rest.
(6)
Customer Mail Sales orders Entered sales orders Entered sales order data Sorted sales records Sales commission report Sales manager Sales order form file 1. Open mail 2. Enter sales order data 3. Sort sales order s 4. Compute sales commissions
A Data Flow Diagram (Figure 0 Diagram) of a Sales Commission System
(7)
When Drawing a Context
When Drawing a Context
Diagram
Diagram
1. Use only a single process symbol 1. Use only a single process symbol
2. Label the process symbol to represent the 2. Label the process symbol to represent the
entire system entire system
3. Do not number the single process symbol 3. Do not number the single process symbol
4. Include all terminators for the system 4. Include all terminators for the system 5. Show all the data flows between the 5. Show all the data flows between the
terminators and the system terminators and the system
(8)
Sales Commission
System Customer
Sales Manager
Sales
commission report
Mail A Context Diagram of a
(9)
Figure
Figure
n
n
Diagrams
Diagrams
Documents a single process of a DFD in a Documents a single process of a DFD in a
greater amount of detail
greater amount of detail
nn represents the number of the process on the represents the number of the process on the
next higher level that is being documented
next higher level that is being documented
The term “leveled DFDs” describe the The term “leveled DFDs” describe the
hierarchy of diagrams ranging from context
hierarchy of diagrams ranging from context
to the lowest-level figure n diagram
(10)
Figure 4 Diagram of a Sales Commission System
3
4.1 Compute commission
amounts
4.2
Accumulate totals
Sales manager
Sorted sales records
Commission amounts
Sales commission
(11)
How Many Levels to Use?
How Many Levels to Use?
Restrict a single DFD to no more than six to Restrict a single DFD to no more than six toeight processes eight processes
Use another tool to document the lowest Use another tool to document the lowest
level of detail but use no more than a single level of detail but use no more than a single
page. page.
(12)
Data Flow Diagramming
Data Flow Diagramming
Guidelines
Guidelines
1. Label each data flow with a unique name.
1. Label each data flow with a unique name.
2. Keep data flow names constant between levels.
2. Keep data flow names constant between levels.
3. Show proper disposition of records deleted from a data
3. Show proper disposition of records deleted from a data
store.
store.
4. When documenting a computer program, do not include
4. When documenting a computer program, do not include
reads/writes.
reads/writes.
5. Avoid read-only processes.
5. Avoid read-only processes.
6. Write-only processes are permissible when time serves as
6. Write-only processes are permissible when time serves as
the trigger.
(13)
Structured English
Structured English
Narrative form of computer code Narrative form of computer codedocumentation documentation
Based on PseudocodeBased on Pseudocode
Abbreviated, formalized pseudocode in a Abbreviated, formalized pseudocode in a
particular format that looks like computer particular format that looks like computer
code code
(14)
Structured English
Structured English
Guidelines
Guidelines
1) Use a verb when describing each processing 1) Use a verb when describing each processing
strip.
strip.
2) Supplement verb with one or more objects 2) Supplement verb with one or more objects
when necessary.
when necessary.
3) Use only three constructs of programming.3) Use only three constructs of programming.
– SequenceSequence – SelectionSelection – RepetitionRepetition
(15)
Structured English
Structured English
Guidelines [cont.]
Guidelines [cont.]
4) Use only data names defined in the data 4) Use only data names defined in the data
dictionary. dictionary.
5) Use uppercase for all data names and 5) Use uppercase for all data names and
computer syntax. computer syntax.
(16)
Structured English
Structured English
Guidelines [cont.]
Guidelines [cont.]
7) When documentation is subdivided into 7) When documentation is subdivided into
modules, use the first line of each module modules, use the first line of each module
for an identifying label and leave at least for an identifying label and leave at least
one blank line in-between. one blank line in-between.
8) Restrict each module to a single entry 8) Restrict each module to a single entry
and exit point. and exit point.
(17)
Structure English Example
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
(18)
Summary
Summary
Process modeling is an important part of Process modeling is an important part of
system design
system design
Various techniques exist for process modelingVarious techniques exist for process modeling
– DFDsDFDs
– Structured EnglishStructured English
Manager can use Structured English and Manager can use Structured English and
DFDs to communicate system requirements
(1)
Structured English
Structured English
Narrative form of computer code Narrative form of computer code
documentation documentation
Based on PseudocodeBased on Pseudocode
Abbreviated, formalized pseudocode in a Abbreviated, formalized pseudocode in a
particular format that looks like computer particular format that looks like computer
code code
(2)
Structured English
Structured English
Guidelines
Guidelines
1) Use a verb when describing each processing 1) Use a verb when describing each processing
strip. strip.
2) Supplement verb with one or more objects 2) Supplement verb with one or more objects
when necessary. when necessary.
3) Use only three constructs of programming.3) Use only three constructs of programming.
– SequenceSequence – SelectionSelection – RepetitionRepetition
(3)
Structured English
Structured English
Guidelines [cont.]
Guidelines [cont.]
4) Use only data names defined in the data 4) Use only data names defined in the data
dictionary. dictionary.
5) Use uppercase for all data names and 5) Use uppercase for all data names and
computer syntax. computer syntax.
(4)
Structured English
Structured English
Guidelines [cont.]
Guidelines [cont.]
7) When documentation is subdivided into 7) When documentation is subdivided into
modules, use the first line of each module modules, use the first line of each module
for an identifying label and leave at least for an identifying label and leave at least
one blank line in-between. one blank line in-between.
8) Restrict each module to a single entry 8) Restrict each module to a single entry
and exit point. and exit point.
(5)
Structure English Example
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
(6)
Summary
Summary
Process modeling is an important part of Process modeling is an important part of system design
system design
Various techniques exist for process modelingVarious techniques exist for process modeling
– DFDsDFDs
– Structured EnglishStructured English
Manager can use Structured English and Manager can use Structured English and
DFDs to communicate system requirements