Modern Systems Analysis and Design

1
????? ?????? ????? Modern Systems Analysis and
Design
?????? ?????? ???????????
???????? ?? ????? ??? ???? ????-

• 8
• ????? ??????? ?????? (????? ?????????)
• Structuring System Requirements
• Process Modeling

8.1
2
????? - ????? ????????? - Process Modeling

• ??? ????????? (?????? ??? ???????? ?????????
  ???????? ?????? ??? ?????? ??????? ???????
  ???????) ???? ???? ?? ?????
• ?????? ???? ????????Data flow diagrams (DFD)
• ???? ???? ???????? ??? ???????? ????????
  ?????????? ????????? ??????? ???? ??????
• ????? ????? ?? ??????
• ?????? ????????? ??????? ???? ????? ?????
  ?????????
• ????? ???????? ???? ??? ?????????
• ????????
• ?????? ?? ?????? ???? ???????? ??????? ????????

8.2
3
Process Modeling

• ???? ... ????????
• ???? ?????? Context data flow diagram (DFD)
• ???? ???? ????? ?????? Scope of system
• ???? ?????? ??????DFDs of current system
• ???? ?????? ??????
• ???? ?????? ?????? ??????? DFDs of new logical
  system
• ????? ?? ??????????? Technology independent
• ???? ???? ???????? ??????? ?????????? ????????
  ?????? ??????
• ????? ?????? ????? ???????? Project dictionary
  and CASE repository

8.3
4
Data Flow Diagramming Mechanics

• ????? ???? 4 ???? Four symbols are used
• See Figure 8-2
• Two different standard sets can be used
• DeMarco and Yourdan
• Gane and Sarson

8.4
5
Figure 8-2Comparison of DeMarco Yourdan and
Gane Sarson DFD symbol sets
8.5
6
Data Flow Diagramming Mechanics

• ???? ???????? Data Flow
• ???? ????
• ?????? ??? ?? ???? ???? ?????? ????????
• ???? ???????? Data Store
• ???? ???????? ??????? (???? ?? ??? ???? ????
  ?? ???? ???????) File folder Computer-based
  file Notebook
• ??? ???? ?????? ???? ???? ???? ???????? ?? ??????

8.6
7
Data Flow Diagramming Mechanics

• ??????? Process
• ???? ????? ?? ?????? ???? ??? ??? ???????? ?????
  ?????? ???? ?? ???? ?? ????
• ????? ?????? ????
• ?????? ?? ?????? Source/Sink
• ???? ???? ( ? - ?? ) ???? ????????
• ?????? ???? ??? ???? ?????
• ???? ????? ?? ??????
• ??? ??? ????
• ??? ???? ???? ????? ? ??? ?????? ?? ????? ???
  ???? ???

8.7
8
??????? Data Flow Diagramming Definitions

• ???? ?????? Context Diagram
• ?????? ???? ????? ?????? ????????? ???????? ????
  ???? ?? ?????? ????? ???????? ???????? ????? ????
  ??????
• ???? ??????? ?????? Level-O Diagram
• ???? ????????? ???????? ????????? ???????? ??????
  ???????? ???????? ???? ?????

8.8
9
????Developing DFDs An Example

• ???? ????? ??? ?????? Hoosier Burgers automated
  food ordering system
• ???? ?????? ????? ???? ????????Context Diagram
  (Figure 8-4) contains no data stores
• ???? ??????? ????? Next step is to expand the
  context diagram to show the breakdown of
  processes (Figure 8-5)

8.9
10
Figure 8-4Context diagram of Hoosier Burgers
food ordering system
8.10
11
Figure 8-5Level-0 DFD of Hoosier Burgers food
ordering system
8.11
12
????? ??????? Data Flow Diagramming Rules

• ???????? ?????? ????? ??? ????????
• ????? ????? ?????? ????????
• ???? ????? ????? ????? ???????? ?? ????? ?????
  ?????? ???????? ??? ?? ???? ?????? ????

• ???? ???????? Data Store
• ?? ???? ?????? ???????? ?? ???? ???? ???? ?????
• ?? ???? ?????? ???????? ?????? ?? ?????? ?????
  ??????
• ??? ?? ???? ?????? ??? ???? ??????
• ??????? ????? ???????? ?? ???

• ??????? Process
• ?? ???? ????? ??????? ???(a miracle)
• ?? ???? ????? ??????? ??? (black hole)
• ??????? ?? ???

8.12
13
????? ??????? Data Flow Diagramming Rules

• ?????? ?? ??????Source/Sink
• ?? ???? ?? ????? ???????? ?????? ??????
• ??????? ?? ???

• ???? ???????? Data Flow
• ??? ????? ???? ??? ??? ??????
• ?????? ???? ?????? ???? ?? ??? ???????? ???? ??
  ???? ??? ???????

8.13
14
Data Flow Diagramming Rules

• ???? ???????? Data Flow
• A join means that exactly the same data comes
  from any two or more different processes, data
  stores or sources/sinks to a common location
• A data flow cannot go directly back to the same
  process it leaves
• A data flow to a data store means update
• A data flow from a data store means retrieve or
  use
• A data flow has a noun phrase label

8.14
15
????? - ????? Decomposition of DFDs

• ??????? ??????? Functional decomposition
• ??????? ?? ???? ???? ??? ??? ??????? ???????
• ????? ?????
• ??? ????? ???? ?????? ??????? ?? ?????? primitive
  
• ?????? ????????? Level-N Diagrams
• ???? ?? ????? ???????? ????? ?? ????????? ???????
  ?? ??????? ???????

8.15
16
????? ?????? - Balancing DFDs

• ??? ??????? ? ??? ???????? ??? ???????? ?????????
  ?????? ???? ?? ??????? ??????
• ???? Hoosier Burgers
• In Figure 8-4, notice that there is one input to
  the system, the customer order
• Three outputs
• Customer receipt
• Food order
• Management reports

8.16
17
??????? Balancing DFDs

• ???? ??? ???????
• Notice Figure 8-5. We have the same inputs and
  outputs
• No new inputs or outputs have been introduced
• We can say that the context diagram and level-0
  DFD are balanced
• ???? ??? ??? ???????
• Figure 8-10 ( In context diagram, we have one
  input to the system, A and one output, B )
• Level-0 diagram has one additional data flow, C
• These DFDs are not balanced

8.17
18
???? ??? ??? ??????? Figure 8-10An unbalanced
set of data flow diagrams(a) Context diagram(b)
Level-0 diagram
8.18
19
??????? Balancing DFDs

• ???? ???? ???? ???? ??? ?????? ?????? ?? ????
  ?????? ??? (see Figure 8-11)
• ??????? ?????? ??? 4 ????? ?????? (See Table 8-3)

8.19
20
????? ?????? - Four Different Types of DFDS

• ??????? (??????) ?????? Current Physical
• ????? ??? ??????????? (????? ????????) ????
  ??????? ??????? ???????? ???????? ?? ?????? ???
  ???? ?????? ?? ??????? ???????
• ??????? ?????? Current Logical
• ??????? ??? ??? ???????? ?????????? ???? ????
  ????? ????? ?? ??? ??? ???????? ???????
• ??????? ?????? New Logical
• ?? ????? ??????? ??????? ??? ??????? ???????
  ????? ????? ?????? ?????? ????? ???? ????????
• ??????? ?????? New Physical
• ????? ?? ???? ?????? ??????? ????? ?? ??????
  ??????

8.20
21
??????? ???? ?????? Guidelines for Drawing DFDs

• ???????? ????????? Completeness
• ??? ???? ?? ???????? ?? ??? ???? ??? ?? ?????
  ??????
• ??????? ???????? Consistency
• ??? ??????? ??? ?? ?? ????? ?? ????? ?? ????
  ?????????
• ????? Timing
• ????? ?? ??? ?????? ??? ???? ?????? ?? ???? ????
  ?? ????? ?? ??? ???? ?? ?? ?????
• ??????? ??????? Iterative Development
• ???? ?? ???? ??? ???????? ??? ???? ?? ??????? ???
  ??? ??? ???? ??? ?????? ???????

8.21
22
??????? ???? ?????? - Guidelines for Drawing DFDs

• ??????? ??????? ?? ?????? Primitive DFDs
• ??? ????? ??????? ???? ????? ???? ?????? ??
  ??????? ?? ????? ???????
• ????? ??? ???????
• ??? ?????? ??? ????? ??????? ??? ???? ???? ????
  ?? ????? ?????? ????? ?? ????? ?? ?????? ?????
  ????????
• ????? ???? ?? ???? ?????? ???? ???? ????
• ????? ?? ???? ???????? ??????? ????
• ??? ??? ?????? ???????? ???? ?????? ??? ?????
  ????????
• ????? ???? ???? ?? ?????? ?? ???? ??? ????? ???
  ?????
• ????? ???? ?? ???? ????? ????? ??? ???? ??
  ??????? ?? ?? ?????????

8.22
23
??????? ?????? ?????? ???????Using DFDs as
Analysis Tools

• ????? ?????? Gap Analysis
• ??????? ????? ??? ???????? ?? ???? ?? ???????? ??
  ????????? ???? ???? ????
• ??? ????? ?????? ???? ????? ???????? ?? ???? ???
  ??????

8.23
24
??????? ?????? ?? ???????Using DFDs in Business
Process Reengineering

• Example IBM Credit ????
• See Figure 8-20 before reengineering
• Credit approval process required six days before
  BPR
• Figure 8-21 depicts DFD after reengineering
• IBM was able to process 100 times the number of
  transactions in the same amount of time

8.24
25
Oracles Process Modeler and Functional Hierarchy
Diagrams

• Process Modeler
• Unique to Oracle
• Similar to DFDS but outputs and methods differ in
  several ways.
• Table 8-4 illustrates differences
• Functional Hierarchy Diagrams
• Picture of various tasks performed in a business
  and how they are related
• Tasks are broken down into their various parts
• Does not include data flows

8.25