ITM 410 Chapter Notes - Chapter 4: Data Flow Diagram, System Context Diagram, Flowchart

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Published on 5 Feb 2013
Chapter 4 Documenting Information Systems
Reading Systems Documentation
Refer to figure 4.1 for Data Flow Diagram (DFD) Symbols on pg 104
Reading Data Flow Diagrams
Data flow diagram (DFD) is a graphical representation of a system
o It depicts a system’s components, the data flows among the components & the
sources, destinations & storage of data
Context Diagram
Context diagram is a top-level or least a detailed diagram of a system depicting the
system & all its activities as a single bubble & showing the data flows into & out of the
system & into & out of the external entities
o External entities are those entities outside the system that send data to or receive
data from the system
o Refer to figure 4.2 on pg 105
Physical Data Flow Diagram
Physical data flow diagram is a graphical representation of a system showing the
system’s internal & external entities & the flows of data into & out of these entities
o Internal entities is an entity within the system that transform data (ex. accounting
clerks, departments & computers)
o Physical DFDs specify where, how & by whom a system’s activities are
accomplished but does not specify what activities are taking place
Refer to figure 4.3 on pg 106 and read the example
Logical Data Flow Diagram
Logical data flow diagram is a graphical representation of a system showing the
system’s processes (as bubbles), data stores & the flows of data into & out of the
processes & data stores
o Logical DFDs specifies what activities the system is performing without having to
specify how, where or by whom the activities are accomplished
o Advantage of a logical DFD
We can concentrate on the activities that a system performs (what the
system performs instead of trying to figure out how, where or by whom)
Refer to figure 4.4 on pg 107
Logical DFDs are also known as level 0 diagram
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