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3SL Reference - Process Flow Diagram (PFD)

Process Flow Diagram (PFD)

Each Process Flow Diagram (PFD) shows a particular task or process that the system can perform, known as a flow. A system will provide many process flows, and indeed may perform many process flows simultaneously. Each process flow connects functions in the system model along a timeline, any manual operations performed by users, and operations performed by external systems.

The operation is the basic unit of a process flow, and is therefore the principal symbol used on a PFD. Remaining PFD symbols are used to describe the timeline that links the operations.

PFDs provide four types of operation:

  • Operation
  • System
  • User
  • Agent