Name: Jecca Cervero

Section: O0C

            Book: Systems Analysis And Design /Fifth Edition

            Author: Kenneth E. Kendall, Julie E. Kendall

            Reference No.: QA 76.9 S88 K45 2002

Chapter:  Chapter 9

Quote: To begin a data flow diagram, the system analyst needs to collapse the organization’s system narrative into a list with four categories-External entity, Data flow, Process, and Data store.

Review:

Developing Data Flow Diagrams

To start drawing the diagram flow you may:

1. start with the data flow from an entity on the input side. Ask questions

2. work backwards from an output data flow. Examine the output fields on document on screen.

3. Examine the data flow to or from a data store.

4. Analyze the well-defined process. Look at what input data the process needs and what output it produces. Then connect the input and output to the appropriate data stores and entities.

5. Take note of any fuzzy areas where you are unsure of what should be included or of what input or output is required.

To summarize the steps involved in successfully completing data flow diagrams, first, the systems analyst need to conceptualize data flows from a top-down respective. The system analyst needs to collapse the organization’s system narrative into a list with four categories:

·        External entity

·        Data flow

·        Process

·        Data store

Drawing diagram 0

Diagram 0 is the explosion of the context diagram and may include up to nine processes.

Creating the Context Diagram

Context diagram-is the highest level in a data flow diagram and contains only one process, representing the entire system.

Creating Child Diagrams (More detailed level)

Each process on diagram 0 may in turn be exploded to create a more detailed child diagram. The process on diagram 0 that is exploded is called the parent process, and the diagram that result is called the child diagram.

Checking the Diagrams For Errors

Several common errors when drawing data flow diagrams are as follows:

1.     Forgetting to include a data flow or pointing an arrowhead in the wrong direction

2.     Connecting data stores and external entities directly to each other

3.     Incorrectly labeling processes or data flow

4.     Including more than 9 processes on a data flow diagram

5.     Omitting data flow

6.     Creating unbalanced decomposition in child diagram