IT3 System Development Life Cycle [SDLC] SDLC System Development REASONS for SDLC Make sure that the computer system works well Makes sure that the computer

IT3 System Development Life Cycle [SDLC]

SDLC

System DevelopmentREASONS for SDLC•Make sure that the computer system works well

•Makes 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


SDLC

SCENARIOBusinesses would PAY professional companies for the support, backing and advice for their IT Systems.

These could be NEW businesses starting out and in need of advice in setting up a BRAND NEW COMPUTER SYSTEM or Businesses with existing systems that need support or advice


SDLC

In School we use a company called CYNNAL with our support and advice on our IT system.

THEY ARE responsible FOR OUR

SDLC


SDLC

System DevelopmentAll organisations have various systems to deal with different parts of the company:- wages, stock, accounts etc

A SDLC are a sequence of activities used to look at systems used within organisations.

These are used if any developments, changes or improvements are required for the system.

There are specific ACTIVITIES performed to carry out a SDLC - SIX STEPS

Investigation

Analysis

Implementation

Design

Maintenance

EvaluationThis is CYCLIC - continual system of looking at the system


SDLC

1. Identify & Investigate

2. Analyse

3. Design

4. Implement

5. Maintenance

6. Evaluation

SIX STEPS used to Perform a System Development Life Cycle


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[i] Existing Hardware and SoftwareWhat does the organisation have already - what can be used again and what will have to be replaced.[ii] Definition of the scope of the present systemWhat will the new system have to do - types of outputs – forms, graphs etc. How will data be inputted - new system might require a barcode system.[iii] Major data processing functions and processes High level (contextual view) data flow - Diagram of how data is processed within the system[iv] Identification of problems with the present systemThe present system might not have facility for inputting data by barcode.School might be thinking of using a new registration system using biometric fingerprint device - the existing system might not support this system.

1. INVESTIGATION Areas that will be looked at:-


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[iv] Identification of problems with the present systemThe present system might not have facility for inputting data by barcode.School might be thinking of using a new registration system using biometric fingerprint device - the existing system might not support this system.[v] Identify user requirements for the new systemThere might be new areas to be developed - company might be thinking of e-commerce as a new area.[vi] Analysis of costs and benefits of the new system.What will it cost in terms of money - training staff, buying new equipment hardware & software.

1. INVESTIGATION Areas that will be looked at:-


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1. INVESTIGATION

Before the work can start the system must be INVESTIGATED

Information about the system must be collected, this can be done by:-


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1. INVESTIGATION

•Interviews

Talk with managers and staff on how the existing system works and what are the problems, what possible improvements could be made.

•Observations

Look at how the workers interact with the system, what do they do? How do they use the system?

•Looking at records or documents

Look at outputs, printed forms etc, Orders created, manuals, user documents, job descriptions.

•Questionnaires

Hand out questionnaires to employees, must be carefully designed, poor questions - poor results - no good.


SDLC

CREATING A FEASIBLITY REPORT

After all the investigation is carried out a FEASIBILITY REPORT is produced to see if the new proposals or changes can be made. No point beginning major changes and finding out that the system is not possible to achieve or would cost too much.

A Feasibility Report should include:-

[i] User requirements - what is required for the employees using the system

[ii] Existing system - what are the existing hardware and software used – possible to use again or new hardware and software needed.

[iii] Processing issues - what needs to be done.

[iv] Problems - limitations and issues with existing system

[v] Costs - how much will this cost, equipment, staffing,

1. INVESTIGATION


SDLC

2. ANALYSIS

This is the process of going ahead with the new system after the investigation work and feasibility report has been produced.

This is the stage where further investigation to the system is required and the existing system is analysed in detail -

Tools and techniques used to analyse systems

- The existing system can be analysed by using a DFD - Data Flow Diagram

and

- Entity Relationship models – how data is related in the system


SDLC

The Analysis will look at the following areas:-

1. How Data flows and is used within the Company

2. What type of data needs to be stored and how it is arranged

3. Structure of data tables

2. ANALYSIS


SDLC

2. ANALYSIS

PROCESS

DATA FLOW

DATA STORE

SOURCE

These are the symbols used when creating a Data Flow Diagram


SDLC

Food ordering system

0

CUSTOMER KITCHEN

RESTAURANT MANAGER

Food Order

Management Reports

Customer Order

Receipt

Level 0 Context Diagram

2. ANALYSIS This is an example of how data flows within a Burger Bar


SDLC

1.0

Receive and transform

Customer Food Order

2.0

Update Inventory

file

3.0

Update Goods

Sold file

4.0

Produce Management

Reports

CUSTOMERKITCHEN

RESTAURANT MANAGER

Food Order

Customer Order

Receipt

Management Reports

Goods Sold File

D1D2 Inventory File

Goods

Sold

Inventory

Data

Goods Sold Data

Inventory Data

Daily Goods Sold Amount

Daily Inventory Depletion Amounts

LEVEL 1 DIAGRAM


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ENTITY - An object of the real world, can be a person, product, customer, place

ATTRIBUTE - A single item of data which is a fact about an Entity

ENTITY ATTRIBUTE

PUPIL

- Class

- D/O/B

- Subject

- Number

2. ANALYSIS


SDLC

RELATIONSHIPS

Relationship between entities in a system;

Can be:-

ONE to ONE

ONE to MANY

MANY to MANY

ENTITY 1 ENTITY 2

ENTITY 1 ENTITY 2

ENTITY 1 ENTITY 2

2. ANALYSIS


SDLC

CUSTOMER

ORDER BOOK

DELIVERY

ORDER BOOK

Simple diagram of how relationship works for Book ordering system

This diagrams shows that it is possible to make many orders on many books

Many to Many

2. ANALYSIS


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ATOMIC AttributesMr John Jones

Data must be atomic within databases.

For example the above data contains TITLE, FIRST NAME & SURNAME

Difficult to create a search for all people with Jones Surname

The data must be broken down to THREE Atomic Attributes

1. TITLE

2. FIRST NAME

3. SURNAME

2. ANALYSIS


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DATA DICTIONARY TABLES

Data is broken down stating the following:-

•Contents

•Field names

•Data types

•Relationships

•Text field length

2. ANALYSIS


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3. DESIGN

This activity involves working out what will be needed for the system to work:-

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.

Design work will include guidelines for all of the above and how the system will work


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4. IMPLEMENTATION

This is the stage where the system is actually built.

- Hardware will be bought and installed, computer programmers will be installing software and programmes

- Testing the system at all levels - security, with real data.

- Training of staff to use the system


SDLC

4. IMPLEMENTATION CHANGEOVER METHODS

In order to move to a new system different methods can be used to changeover from the old system to a new system. Choosing which method depends on the organisation.

•Is there an existing system

•New location or different locations

1.DIRECT CHANGEOVER

2.PARALLEL CHANGEOVER

3.PHASED CHANGEOVER

4.PILOT CONVERSION


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4. IMPLEMENTATIONDIRECT CHANGEOVER

Direct Changeover (e.g. done over a weekend) is fast and efficient but there is great disruption if the system turns out to be less than perfect. Company cannot carry on if the system doesn’t work.

Unless the employees are trained before hand they wouldn't be able to use the system effectively until they get used to it - need training


SDLC

4. IMPLEMENTATION PARALLEL CHANGEOVER

Parallel Conversion is where the old system continues to be used alongside the new system for a few weeks. This means staff have double the work to do. However, the great advantage is that results from the old system can be tested against results from the new system.

Employees can still use the old system until they get used to the new system.

Business is able to carry on.


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4. IMPLEMENTATIONPHASED CONVERSION

Parts of the system is done gradually. If there is a problem with the new set up, then the problem can be sorted out before moving on to the next phase.

Only suitable if there is an existing system


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4. IMPLEMENTATIONPILOT CONVERSION

Pilot Conversion is where 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.


SDLC

5. MAINTENANCE

Once the system has been set up, it needs to be maintained.

•Train staff

•Update software & hardware

•Software bugs sorted out

•System crashes sorted out


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5. MAINTENANCE

Types of maintenance that can be carried out:-

1. Perfective

Fine tuning of system, improving speed, adding extra features.

2. Adaptive

Adapt the system slightly to accommodate new requirements, company might require a new method of inputting data

3. Corrective

Faults in the system, software bugs, download patches to correct software problems


SDLC


1. Perfective - examples

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

5. MAINTENANCE


SDLC


2. Adaptive - examples

Adapt the system slightly to accommodate new requirements, company might require a new method of inputting data.

Change in business - new line in products, system must be adapted to cater for this.

New legislation – laws - Data Protection,

New printers - need new drivers to work the printers


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3. Corrective

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.

5. MAINTENANCE


SDLC

5. MAINTENANCE

USER 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 a Programmer level, flowcharts of system specification of system, user interface design. Programming language, installation guide


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6. EVALUATION

This stage takes place a few weeks after the system has been built or set up. Evaluation will look at the following areas:-

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


SDLC

6. EVALUATION

Tools used to gather evaluation information:-Quantitative testing - performance and speed of system. How easy is the system to use - marks out of 10 by users. [Quantitative can be measured ]

Error logging - system can register every time part of the system fails. The analyst can look at these and determine what needs to be done to improve the system.

Questionnaires - Ask users and business questions on how satisfied they are with the system. Ease of use, dependability etc.


SDLC

POST IMPLEMENTATION COSTS

When the system has been completed businesses are aware that there will be ongoing costs with a system, they will have to plan ahead and budget for these.

1.Training of staff2.Upgrading of hardware & Software3.Correction of software bugs4.Help desks and support staff5.Modification of system


SDLC

1. The full range of user requirements has not been met, so the system does not live up to user expectations.

2.Change in business needs means system cannot deal with new demands placed on it.

3. Failure to supply users with the information they require.

4. User interface causes many user problems with increased help-desk use.

BUSINESS MIGHT BE DISSATISFIED WITH SYSTEM BECAUSE OF THE FOLLOWING:-


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5. Problems with the software or system crashing owing to lack of rigorous testing.

6.Network performance or speed of access to stored data becomes unacceptable as more users are added to the system.

7. Modifications to the system are needed regularly and the system needs replacement with a new one.

8.Too much time is spent updating to the new system.

BUSINESS MIGHT BE DISSATISFIED WITH SYSTEM BECAUSE OF THE FOLLOWING


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BUSINESS MIGHT BE DISSATISFIED WITH SYSTEM BECAUSE OF THE FOLLOWING

9.The cost of user support is too high.

10. There are security breaches which were not envisaged when the system was first developed.

11.Speed – hard drive filling up – demands of software

12. Fashion – hardware satisfaction

13.Compatibility issues using newer versions of software

Documents

IT3 System Development Life Cycle [SDLC] SDLC System Development REASONS for SDLC Make sure that the computer system works well Makes sure that the computer