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Designing the new system. The Systems Life Cycle: Design. So far, our analyst has…. Collected information on how the current system works Established inputs, processes & outputs Recorded information Identified problems Identified suitable hardware & software

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Designing the new system

Designing the new system

The Systems Life Cycle: Design


So far our analyst has
So far, our analyst has….

  • Collected information on how the current system works

  • Established inputs, processes & outputs

  • Recorded information

  • Identified problems

  • Identified suitable hardware & software

  • Identified user & information requirements


In this next stage the following are designed
In this next stage, the following are designed:

  • Inputs to the system

  • Outputs from the system

  • Files/databases needed to store the data

  • The processing required to produce the outputs

  • Any validation required

  • The data needed to test the system


Designing data collection forms screen layouts
Designing data collection forms/screen layouts

  • DCFs can be paper based or on screen

  • Need to take great care – why?

    • Easy for workers to fill

    • Easy for secretary to read

    • Eg one box per character

    • Minimise errors

    • Requirements must be clear

    • Design may depend on user requirements/required output


Designing screen layouts
Designing screen layouts

  • Screens must be easy to use

  • Attractive to look at

  • Limit possible errors

  • Guidelines

  • Navigation

  • Input devices


Designing report layouts
Designing report layouts

  • Influenced by views of user

  • Also by user requirements

  • Attractive

  • Not over-elaborate

  • Instructions for navigation

  • Output format (graphs/lists/reports/tables)

  • Medium (paper/screen/sound)


Designing report layouts1
Designing report layouts

  • Layout: who sees it? – users and customers, so need to consult with Company

  • Easy to read

  • Professional

  • Style: house style

  • 3 or 4 different designs for approval


Designing screen displays
Designing screen displays

  • Keep simple & consistent

  • Not over-elaborate

  • Attractive

  • Navigation

  • Users: no need for advertising

  • Instructions for use


Designing data file structures
Designing data & file structures

  • Master files

  • Transaction files

  • Field names

  • Field types

  • Field lengths

  • Validation rules

  • Field descriptions

  • Key field

  • Relationships

  • Test plan


Designing validation routines
Designing validation routines

  • As many data validation routines as possible – why?

  • Range checks/length checks/presence checks/format check/


Designing other ways of reducing errors
Designing other ways of reducing errors

  • Reducing volume of input data (coding)

  • Direct data entry methods


Specifying the required hw sw
Specifying the required HW & SW

  • Final stage

  • Earlier: general recommendations

  • Now: specific

    • May include supplier details

    • Volume of data may determine input/output devices

    • Storage: indexed sequential or sequential?


Software build or buy
Software: Build or Buy?

  • Off the shelf or

  • Purpose built


Off the shelf
Off the shelf

Advantages:

  • Mass produced so cheaper

  • Available straight away

  • Rigorously tested

  • Helplines etc available

Disadvantages:

  • Cannot be adapted/difficult to adapt

  • May have distracting extra features (eg Office Paperclip)

  • May not match existing system & software


Purpose built
Purpose built

Disadvantages:

  • Cost

  • Testing limited to perception of programmer

  • Support limited to team of programmers

  • Time to develop

Advantages:

  • Designed specifically for the task

  • Does not need to be adapted

  • Programmers can make any required changes


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