Data Flow Diagram (DFD)

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Data Flow Diagram (DFD)
Chapter 2-1

• ??? ...?????????????? ????????
• Kate_psu08_at_hotmail.com

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Concept System Analysis

• ???????????????????????
• Data Flow Diagram (DFD)
• ??????????????????????? ??????
• ??????????????????? ???????????
• ?????????????????????????
• Context Diagram (Level 0)
• System Diagram (Level 1)
• Lower Level DFD

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System Analysis

• ???????????????????????
• ??????????????????????????????????????????????
  ???????????????????????????????????????
• ????????????????????? (Logical Model)
• Data Flow Diagram (DFD) ?????????????????
  ???????????????? ???????????????????
  ????????????? ????? ?????????
• ??????????????????? (Data Model)
• E-R Diagram ????????????????????????????????

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????????? Process
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Process Hierarchy chart
Hierarchy chart ??? ???????????????????????????
?????????????????????? ??????
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Data Flow Diagram (DFD)

• DFD ?????????????????
• DFD ???????????????????????????????? data ???
  process ???????????????????
• DFD ??????????????????????????? logical
  model ??????????????? process ???????????????????
  ? ???????????? process ??????????????????????
  (??? what ????????? how)
• ???????????? DFD ??????????????????????? 2
  ???
  
• Gane and Sarson
• Yourdon

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Data Flow Diagram (DFD)

• ????????????????????????????? DFD ?????? 4 ???
  ???
• 1. Process
• 2. Data flow
• 3. Data store
• 4. External entity
• DFD ????????????
• 1. ??????????????????
• 2. ??????????????
• 3. ?????????????????????
• 4. ?????????????????????????????????????????????
  ????

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?????????????????????????????

• Process symbol
• ??????? ??????????????? ???? ?????
• ????????????????????? (Verb) ???? ?????????
  ??????? ??????? ???????????
• ???????????????????????????????? ?????????????
  ???????????????? process ?????????????????
  process description
• ??????????? (input) ??? ??? ??????? (output)
  ????????? ?????????????????? process ????

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?????????????????????????????

• Data flow symbol
• ????????????????? ?????????????????????????
• ???????????????????????????????? 1 ???
• ????? process ??????????????? 1 data flow
  ???? ???? 1 data flow ???

Customer
Order
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?????????????????????????????

• Data store symbol
• ?????????????????????????????????? ???? ????????
• ???????????????????????????????????????????
• ????????????????????? process
• ??????????????? 1 data flow ???? ???? 1 data
  flow ???

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?????????????????????????????

• External entity symbol
• ?????????????????????????
• ????????? ???????? ?????? ???? ??????
  ???????????????????? ???
• ????????????????????????
• ?????????????????????????? terminators ????
  source ???? sink

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??????????????????????????????

• Process
• Process ?????????? Input ??? Output Data flow
• ????? input ??????????
• ????? output ??????????
• ??????? process ???????????????? ????
  ?????????????

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??????????????????????????????

• Data Store
• ????? data flow ??? data store ????? data store
• ????? data flow ??? external entity ????? data
  store
• ????? data flow ??? data store ????? external
  entity
• Data store ????????????????? ????
  ????????????????

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??????????????????????????????

• External Entity
• ????? data flow ??? external entity ?? external
  entity
• ??????? external entity ????????? ???? ??????
• Data FlowData Flow
• data flow ?????????????????????????????
• data flow 11 ????????????????? 22 ????
  ??????????????????????????? ???
• ????? 2 process2 process
• ????? data flow ?? join ??????????????????????

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??????????????????????????????

• Data FlowData Flow (???)
• Data flow ?????????? process ????
• Data flow ??????? data store ?????????? update
  ?????????
• ???????????????????
• ??????????????????????

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?????????????????????????
(??????????????????)
(???????????)
(??????????????)
(????????????????????????)
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(???????????)
(??????????????)
(???????????????????)
(?????????????)
(???????????????????????????)
(???????????????????????)
(????????????????????)
(??????????????????)
(??????????? )
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Context Diagram (Level 0)

• ????????????????? DFD ?????????????????
  ?????????????????????
• ??????????
• ???????????? 1 process ???????? ??? process
  ??????????????????????????????
• ???????????????? ????? process ??????????? 0
• context diagram ????????????????????? ???
  external, process ??? data flow
• ?????????? data store ??????????

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System Diagram (Level 1)

• ??????????????????????????????????????????? ???
  process
• ????????
• ??????????????????????????????? context diagram
  
• ???????????????????????????? context diagram
• ???? Process ??????????? , Data Flows ,
  External ??? Data
• Stores

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Lower-Level DFD

• ????????????????????????????????? process ???
  ???????????????
• ?????????????????????? ? ?????????????????????????
  ?
• ?????? Process ???????????? 1
  ?????????????????????????

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