Requirements 1

Structured Analysis MethodStructured system analysis and design

(SSAD)Formal structured dev methodDeveloped by UK Gov. in the 1980’sWe will focus only on analysis

Was used a lot when automating existing manual systems

Main stepsDraw a context diagramDraw DFD of the existing systemDraw DFD of the proposed system and identify the

man-machine boundaryRequirements 2

Context DiagramThe context diagram - represent all external

entities that may interact with a system

Is a DFD with one transform (the system), with all inputs, outputs, sources, sinks for the system identified

The highest level view of a system

Requirements 3

SSAD Main steps1. Draw a context diagram2. Draw DFD of the existing system3. Draw DFD of the proposed system

and identify the man-machine boundary

Example Context Diagram

Requirements 4

DFD of the current systemThe current system is modeled as-is as a

DFD to understand the workingThe context diagram is refined Each bubble represents a logical

transformation of some dataLeveled DFD may be usedGenerally obtained after understanding

and interaction with usersValidate the DFD by walking through with

users

Requirements 5

SSAD Main steps1. Draw a context diagram2. Draw DFD of the existing system3. Draw DFD of the proposed system

and identify the man-machine boundary

Modeling the Proposed SystemNo general rules for drawing the DFD of

the future systemUse existing system understandingDFD should model the entire proposed

system - process may be automated or manual validate with the user

Then establish man-machine boundarywhat processes will be automated and which

remains manualShow clearly interaction between

automated and manual processesRequirements 6

SSAD Main steps1. Draw a context diagram2. Draw DFD of the existing system3. Draw DFD of the proposed

Example – context diagram

Requirements 7

Example – DFD of existing sys

Requirements 8

Example – DFD of proposed system

Requirements 9