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Using data flow diagrams

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Using Data Flow Diagrams Chapt er 7
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Page 1: Using data flow diagrams

Using Data Flow Diagrams

Chapt

er 7

Page 2: Using data flow diagrams

DATA Flow ApproachConceptualize:

“ how data move through the organization ““ the process or transformation that the data undergo “

“ and what are the outputs “

Data Flow Diagrams (DFDs)

ⱷ emphasize the processing of data or the transforming of data as they move through a variety of processes.

Page 3: Using data flow diagrams

Advantages of the Data Flow Approach

Have 4 advantages1. Freedom from committing “technical

implementation of the system”

2. Further understanding of the interrelatedness of systems and subsystems.

3. Communicating current system knowledge to users

4. Analysis of a proposed system to determine if the necessary data and processes have been defined

Page 4: Using data flow diagrams

Conventions used in DFDs

Page 5: Using data flow diagrams

Developing data flow DiagramsDeveloping Data Flow DiagramsUsing a Top – Down Approach

 1. Make a list of a business activities and use it to determine various External entities

Data flows Processes Data stores

2. Create a context diagram that shows external entities and data flow to and from the system. Do not show any detailed processes or data stores3. Draw diagram 0, the next level. Show processes, but keep them general. Show data stores at this level.4. Create a child diagram for each of the processes in Diagram 0.5. Check for errors and make sure that labels you assign to each processes and data flows are meaningful.6. Develop a physical data flow diagram from the logical data flow diagram. Distinguish between manual and automated processes, describe actual files and report by names and add controls to indicate when processes are complete or errors occur.7. Partition the physical data flow diagram by separating or grouping parts of the diagram in order to facilitate programming and implementation.

Page 6: Using data flow diagrams

1st

Basic rules to follow:1. Must have at least one process.2. A process must receive at least one data flow

coming into process and leaving from the process.3. A data store should be connected to at least one

process.4. External entities should not be connected to each

other.

Page 7: Using data flow diagrams

2nd Creating the context

diagram

0

SystemName

Input A

Input B

Output C

D1 Data Store 1 D1 Data Store 1

Entity3Entity

3Entity

2Entity2

Entity1Entity

1

Page 8: Using data flow diagrams

3rd

Drawing Diagram 0

4

General Process

DDD

3

General Process

CCC

2

General Process

BBB

1

General Process

AAA

D1 Data Store 1 D1 Data Store 1 D2 Data Store 2 D2 Data Store 2

Entity1Entity

1

Entity2Entity

2

Entity3Entity

3

Data Flow C

Data Flow B

Record ERecord A

Record A Record E

Data Flow DInput B

Input A Output C

Page 9: Using data flow diagrams

4th Creating Child Diagrams

4General Process

DDD

3General Process

CCC

D1 Data Store 1 D1 Data Store 1

Entity2Entity

2

Record A

Data Flow DInput B

3.2Detailed Process

YYY

D1 Data Store 1 D1 Data Store 1

Record A

TransactionRecord 1

3.2Detailed Process

ZZZ

Detailed Data Flow Z

Data Flow D

D5 transaction File 1 D5 transaction File 13.1

Detailed Process

YYY

TransactionRecord 1

Error

Input B

Page 10: Using data flow diagrams

5th

Checking the Diagrams For Error


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