2. DATA Flow Approach
Conceptualize:
“ how data move through the organization “
“ the process or transformation that the data undergo “
“ and what are the outputs “
Data Flow Diagrams (DFDs)
ⱷemphasize the processing of data or the transforming of data
as they move through a variety of processes.

3. Advantages of the Data Flow
Approach
Have 4 advantages
1. 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

4. Conventions used in DFDs

5. Developing data flow Diagrams
Developing Data Flow Diagrams
Using 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 stores
3. 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.

6. 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.

7. 2nd
Creating the context diagram
0
System
Name
Input A
Input B
Output C
D1 Data Store 1
Entity
3
Entity
2
Entity
1

8. 3rd
Drawing Diagram 0
4
General
Process
DDD
3
General
Process
CCC
2
General
Process
BBB
1
General
Process
AAA
D1 Data Store 1 D2 Data Store 2
Entity
1
Entity
2
Entity
3
Data Flow C
Data Flow B
Record ERecord A
Record A Record E
Data Flow DInput B
Input A Output C

9. 4th
Creating Child Diagrams
4
General
Process
DDD
3
General
Process
CCC
D1 Data Store 1
Entity
2
Record A
Data Flow DInput B
3.2
Detailed
Process
YYY
D1 Data Store 1
Record A
Transaction
Record 1
3.2
Detailed
Process
ZZZ
Detailed
Data Flow Z
Data Flow D
D5 transaction File 1
3.1
Detailed
Process
YYY
Transaction
Record 1
Error
Input B

10. 5th
Checking the Diagrams For Error