Systems Analysis and Design (Level 3)

WednesdaysRochford Campus

Boston College

What is Systems Analysis and Design?

Investigating, understanding and analysing the IT requirements of

business or organisational processes and from all the potential solutions,

designing the chosen one.

Motivation / Key Drivers

Company Year Project Outcome in US Dollars

Hudson Bay (Canada)

2005 Inventory system problems lead to $33.3 million loss

UK Inland Revenue

2004-2005

$3.45 billion tax-credit overpayment caused by software

errors.Avis Europe PLC

(UK)2004 Enterprise resource planning

system cancelled after $54.5 million spent

Ford Motor Co. 2004 Purchasing system abandoned after deployment costing

approximately $400 million

Significant IT project failures, taken from (Dennis et al, ‘Systems Analysis and Design’, 2010 (4th Ed))

Motivation / Key Drivers

Add value to the company i.e. perform work more efficiently, support organisational/business processes and goals increase business profits

Support business growth occurring through acquisitions or increased productivity

Create effective and affordable system solutions first time round

Module Learning Outcomes

Understand the principles of systems analysis and design

Be able to carry out a structured analysis of business systems requirements

Be able to design business systems solutions

Systems Development Life Cycle (SDLC)Group Exercise:

Consider the commissioning of a dress-maker/tailor to produce your wedding dress/ball-gown/suit.

Collaborating in small groups (of say 2-3), try and identify the life stages of the garment before, during and after its creation.

If possible, illustrate these stages in a diagram.

A System Development Life Cycle (SDLC) Illustration

Plan, choose dress

designMeasurements, colour,

material, etc.

Tailor makes pattern

Sews dress

You try it on

Repairs/Alteratio

ns

System Development Life Cycle (SDLC)

• Planning• Analysis• Design• Implementa

tion(Dennis et al.)

• Defined• Investigated• Designed• Implemented

and tested• Maintained

and reviewed(Fishpool and Fishpool)

• Identifying problems, opportunities and objectives

• Determining human information requirements

• Analysing system needs• Designing the

recommended system• Developing and

documenting software• Testing and maintaining• Implementing and

evaluating the system(Kendall and Kendall)

Established SDLC Models

Waterfall V-shaped Spiral Rapid Applications Development

(RAD)

Waterfall Model

V-Shaped Model: Verification and Validation Model

Exercise: Research the V-shaped model and

understand its operation, pros and cons.

Make comparisons with other models

V-Shaped Model: Verification and Validation Model

Rapid Applications Development (RAD) Model

Generic life cycle model determining the problem scope

(also known as the “problem domain”)

gathering requirements writing the specification designing a solution coding the design testing the program code writing documentation reviewing and maintaining the

solution

Investigation needs to focus on:

Data Procedures Future needs Management needs Pros and cons of the existing

system

Requirements AnalysisOnce investigation has revealed what the system currently

does, a requirements analysis and specification are

developed.

The requirements analysis focuses on:

what the new system will need to do (the functionality)

the necessary inputs the processing requirements, the outputs predicted.

At this stage, however, there are no suggestions as to how the

functionality will be achieved. The specification will contain a list of any identified hardware or software requirements, or anything else (e.g. furniture, equipment) that will be needed.

Design (Logical and Physical)

Design starts with an abstract representation of the new system (including data flows, inputs and outputs) using diagrams and supporting text. Logical design specifies what the new system will do. Diagram formats used: Entity relationship models (ERM) for modelling data Data flow diagrams (DFD) for modelling processes and

interactions

In addition, other design tools may be used: Data table or data dictionary Program design tools Network diagrams

Physical design concentrates on the environment within which the new system will be running. It considers storage requirements and database design, performance issues, pseucode, network architecture (including cabling, IP addresses, security…), user-interface design and so on.

System Construction

This involves:

Writing the program, developing the database, installing the network etc.

Documenting the solution (technical and user) Testing the system

This would be undertaken by a development team, working directly from the designs written earlier.

System DeploymentOnce successfully tested, the new system needs to be formally implemented. Users will need to change from the old system to the new.

Four possible changeover strategies may be used: Direct changeover – new system replaces old system

immediately Parallel conversion (or parallel running) – both run

simultaneously for a period Phased conversion – new system is added a bit at a

time Pilot conversion – new system is introduced in just

one branch of a organisation to see how it fairs.

MaintenanceOnce the system is in place, maintenance activities will

begin.

These include:

Corrective action – fixing problems identified in the system

Perfective maintenance – making the system work better

Adaptive maintenance – making changes; expanding the system

Generally these activities will occur chronologically in the order listed.

ReviewThe final stage of the life cycle is the review. All individuals involved in the development of the system will discuss and evaluate the project, the process and the outcome!

This means that each stage of the life cycle will be discussed (good and bad).

It is through this process that analysts, developers and project managers learn.

When undertaking the next project they will feel more confident about what went well and will try and anticipate and avoid anything that went badly.

Eventually, through review activities, a new project may be defined and the whole process will begin again (hence the term ‘life cycle’).