Reasons for sdlc?
- Make sure that the computer system works well
- Make sure that the computer system is up to date
- Make sure that the computer system does what needs to be done
- Continual improvement and development of computer system
What are the six steps used to perform a system development life cycle?
- Identify + investigate
- Analyse
- Design
- Implement
- Maintenance
- Evaluation
What areas will be looked at In the investigation stage?
- Existing hardware and software
- Definition of the scope of the present system.
- Major data processing functions and processes
- Identification of problems with the present system
- Identify user requirements for the new system
- Analysis of costs and benefits of the new system
How is information collected about the system before investigation starts?
- Interviews - talk with managers and staff- how existing system works + what are the problems, possible improvements?
- Observations - look at how workers interact with system, what do they do? How to they use it?
- Looking at records or documents - look at outputs e.g printed forms, orders created, manuals, user documents, job descriptions
- Questionnaires - hand out to employees, carefully designed
What should the feasibility report include?
After investigation
- User requirements
- Existing system - use again or new?
- Processing issues - what needs to be done
- problems - limitations and issues with existing system
- Costs - how much? Equipment? Staffing?
What is an entity? (Analysis)
An object of the real world, can be a person, product, customer, place
What is an attribute? (Analysis)
A single item of data which is a fact about an entity
What relationships In a system can there be?
One to one
One to many
Many to many
What is atomic attributes? (Analysis)
Broken down into three attributes
- Title
- First name
- Surname
Difficult to create a search for all people with JONES surname
Data dictionary tables
Data is broken down stating the following - Contents Field names Data types Relationships Text field length
What happens at the design stage?
- Design of inputs and outputs for the system - user interfaces, data capture, forms, reports, graphs, printouts
- Networks required - best topology for system, speed of data transmission, wireless needs
- Types of hardware and software required - computers or laptops, monitors, printers, input devices
- Personnel issues - staff training needed, organisation of staff
- Security issues - data being stored, must be kept secure
- Types of hardware and software required - computers or laptops, monitors, printers, input devices
- Personnel issues - staff training needed, organisation of staff
- Security issues - data being stored, must be kept secure
What happens at the maintenance stage?
- where the system is actually built
- hardware bought and installed
- computer programmers install software and programmes
- testing system at all levels - security, with real data
- training of staff to use system
What is direct changeover? (Maintenance stage)
- fast, efficient but great disruption if system turns out to be less than perfect
- company cannot carry on if the system doesn’t work
What is parallel conversion? (Implementation)
- old system continues to be used alongside the new system for a few weeks
- this means staff have double the work to do
- great advantage is that the results from the old system can be treated against results from the new system
- business is able to carry on
What’s phased conversion? (Implementation)
- parts of the system is done gradually
- if there is a problem with new set up then the problem can be sorted out before onto the next phase
- only suitable if there is an existing system
What is pilot conversion? (Maintenance)
- part of the organisation pilots the new system and evaluates it
- ideal for very large companies
- areas can be piloted and evaluated before moving on with further changes
Types of maintenance to be carried out?
- perfective - fine tuning of system, improving speed, adding extra features
- adaptive - adapt the system slightly to accommodate new requirements, company might require a new method of inputting data
- corrective - faults in the system, software bugs, downloads patches to correct software problems
Examples of perfective maintenance?
Security issues - new viruses etc
- particular part of the software awkward to use - creating and formatting tables
These could be fine tuned to perfect the system
Examples of adaptive maintenance
- adapt the system slightly to accommodate new requirements, company might require a new method of inputting data
- change in business - new line of produce, system can be adapted to cater for this
- new legislation - laws a - DPA
- new printers - need new drivers to work the printers
Examples of corrective maintenance?
- faults in the system, software bugs, download patches to correct software problems
- problems may become apparent when using the software in real life situations - formulas don’t work out averages etc
What are user documentation and technical documentation?
User documentation
- user manual explaining to the employees how to input data, print reports, create searches, how to save, how to open software. Screenshots and examples are given.
Technical documentation
- these would be at programmer level, flow charts of system specification of system, user interface design. Programming language, installation guide
What areas are looked at in evaluation stage?
- see if system does what the initial requirements asked for
- how happy are the clients
- review cycle - constant checking to make sure that things are still ok
What tools are used to gather evaluation information?
- Quantitative tastings - performance + speed of system. How easy is the system to use n- marks out of 10 by users [quantitative can be measured]
- Error logging - system can register every time part of the system fails. - analyst can look at these and determine what need to be done to improve the system
- Questionnaires - ask users and business questions on how satisfied they are with the system, ease of use and dependability etc
Post implementation costs
- Training of staff
- Upgrading of hardware and software
- Correction of software bugs
- Help desks and support staff
- Modification of the system
(Ongoing costs, plan ahead and budget for them)
