- circle - Process
- arrow - Data flow
- double line - Data Store
- square - Source/Sink
Processes
- work or actions performed on data
- receives input data and produces output
- rule1: can have more than one outgoing data flow or more than one incoming data flow
- rule2: can connect to any other symbol
Data Stores
- represents data that is stored in the system
- processes add or retrieve data from these stores
- only processes are connected to data stores
- name using a noun
Sources/Sinks (external entities)
- External entity that is origin or destination of data
- form the boundaries of the system
Data Flows
- marks movement of data through the system
- connects the processes, external entities and data stores
Different Types of DFDs
- context diagram (Level-0 diagram)
- Level-1 diagram (lower level diagram)
- Level-2 diagram (lower level diagram)
Context Diagram(Level-0 DFD)
- defines the scope of the system by identifying the system boundary
- contain:
- one process
- all sources sinks
- data flows (external)
Lower Level Diagrams
- functional decomposition
State Transition Diagram
- a transition to a different state is caused by the occurrence of an event of by a condition becoming true
- use to show the events which trigger them
- the actions occurring during the transition
source: lecture notes
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