Structured Analysis Method Requirements 1 Structured Analysis

Structured Analysis Method Requirements 1

Structured Analysis Method Structured system analysis and design (SSAD) Formal structured dev method Developed by UK Gov. in the 1980’s We will focus only on analysis Was used a lot when automating existing manual systems Main steps Draw a context diagram Draw DFD of the existing system Draw DFD of the proposed system and identify the man- machine boundary Requirements 2

SSAD Main steps 1. Draw a context diagram 2. Draw DFD of the existing system 3. Draw DFD of the proposed system and identify the man-machine boundary Context Diagram The 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

Example Context Diagram Requirements 4

SSAD Main steps 1. Draw a context diagram 2. Draw DFD of the existing system 3. Draw DFD of the proposed system and identify the man-machine boundary DFD of the current system The current system is modeled as-is as a DFD to understand the working The context diagram is refined Each bubble represents a logical transformation of some data Leveled DFD may be used Generally obtained after understanding and interaction with users Validate the DFD by walking through with users Requirements 5

SSAD Main steps 1. Draw a context diagram 2. Draw DFD of the existing system 3. Draw DFD of the proposed Modeling the Proposed System No general rules for drawing the DFD of the future system Use existing system understanding DFD should model the entire proposed system - process may be automated or manual validate with the user Then establish man-machine boundary what processes will be automated and which remains manual Show clearly interaction between automated and manual processes Requirements 6

Example – context diagram Requirements 7

Example – DFD of existing sys Requirements 8

Example – DFD of proposed system Requirements 9