INFS1200 Notes

Module 2

DFD Concepts

Terminator

• Rectangle labelled with a noun
• A external source / sink of information
• Must have at least one data flow entering or leaving

Data flow

• Arrow labelled with a noun + possible objective
• Carries data from one place in the system to the other
  • Must start or end at a process

Processes

• Rectangle with rounded edges, ID code ontop, and a name underneath
  • 0 is Context Level
  • 1.0, 2.0, 3.0 is Level 0
• An activity that can transform, generate, retrieve, or delete data
• Must have both incoming and outgoing dataflows

Data Stores

• Rectangle with square edges, ID code left, and a filename right
• Must connect only to processes
• Must have at least one incoming and one outgoing flow

DFD Rules

• The input of a process must be different from its outputs