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Unit 7: System Life Cycle (Design (Validation: A process where data is…
Unit 7: System Life Cycle
Analysis
Research or collect data from the current system
Describe the current system (establish the inputs outputs and processing being done)
Identify the problems with the current system
Agree the objectives with the clients
Identify and agree customer requirements
Interpret customer requirements
Produce a cost-benefit analysis
Identify suitable hardware and software
Produce a data flow diagram
Feasibility study
Terms of reference: objectives, boundaries and constraints
Description of the existing system: Identify problems and projected costs
Criteria: Essential requirements and desirable features
Proposed solution: Development plan and cost-benefit analysis
Four common methods used in finding facts
Questionnaire. It is being distributed to workers, clients and system user. This allows quick analysis of data but it is inflexible
Interviews. It involves a Q&A session between the analyst and the customer. It gives opportunity to motivate the interviewee but sometimes it is time consuming.
Observation. Which involves watching personnel using the existing system. This is cheap but people are generally uncomfortable being watched for long hours
Looking at existing paperwork allows the analyst to get some idea of the scale of the problem, memory size requirements, etc. Information can be obtained quick but it is expensive to do
Design
Create the input forms
Make the screen layouts
Design the outputs in the form of screen displays and printed reports
Produce a flowchart for the system
Design a validation rules that could be used
Agree on a file structure
Produce any algorithm
Design a testing plan
Data capture forms
Paper-based form:
Have a heading so its purpose will be clear
Make it clear where the person must fill their answer
Use text box so the amount of information would be limited
Use character box for surnames, telephone number, etc
Use tick box for 2 only answer question (sex-male or female)
Use clear and readable text colours
Computer-based form:
Use of text boxes so data captured will be clear
Use on-screen help when completing the form
Use combo boxes to limit the choices
Use tick boxes which only require one single mouse click
Automatic validation data as it is entered
Control buttons (save, clear entry and NEXT form)
Double-entry box. E.g when entering email address
Screen outputs:
So all of the output fields are correct
So every instruction and description are clear
So the full screen will be utilized
So fonts colour, size and type will be clear
Verification is a way of preventing errors when data is copied from one medium to another
Double entry: Data is entered twice and then is compared by two people
Visual check: Comparing the copied data with the original one
Validation: A process where data is checked to see if it suits several criteria when inputted into a computer
Range check: Check whether the value is acceptable or not
Look up check: Whether the data entered still exist and stored
Length check: If the inputted data contains the required several characters
Character check: To make sure the input data doesn't contain invalid characters
Picture check: To make sure the data is in specific format
Presence check: If the data is present and not been missed out
Consistency check: Check whether the fields tie up with each other
Testing strategy is important so the plan given is agreed by the client, bugs and errors are removed and the software doesn't crash on certain condition
Development and testing
Data categories:
Normal: The data is acceptable and reasonable and has known outcome. E.g. month can be any whole number from 1-12
Extreme: The data is at the limits of acceptability. E.g months can ONLY be 1 OR 12
Abnormal The data is outside the limits of acceptability. E.g. -5 and 7.84 can't be written as month value
Live data: Data with known outcomes which is entered into the new system and the results is compared with those produced from the existing system.
Implementation
One of them is transfer the paper or electronic files to the new system:
Scan in the documents
Key in the data
Download files to new database
Second is changeover to the new system:
Direct changeover. This is immediate but can be disastrous
Parallel running. It is more expensive than direct but when it fails, the old system is still available
Pilot running. It is cheaper than parallel but training is needed
Phased implementation. It is time consuming and failure won't be disastrous
Documentation
User documentation: It is designed to help users to learn how to use the software or system. Example: How to sort data out and print layouts
Technical documentation: It is created to help programmers to make improvements or to repair the system which could consists of hardware and software requirements and validation rules
Evaluation
Things that is considered when evaluating system:
Identify any limitations of the system
Observe users performing tasks
Measure the time taken to complete tasks
Results from evaluation:
Update of hardware due to feedback from users and change is necessitating to do
Update of software because of changes in legislation that might require modification to the software