Requirements Analysis 18. 1 SDM - 2005b518.ppt © Copyright De Montfort University 2000 All Rights Reserved INFO2005 Requirements Analysis Systems Development

Requirements Analysis 18. 1 SDM - 2005b518.ppt

© Copyright De Montfort University 2000All Rights Reserved

INFO2005Requirements Analysis

Systems Development Methodologies

Department of Information Systems



Learning Objectives

Explain what is meant by methodology Examine benefits and limitations Consider alternative views of lifecycles A brief review of exemplar

methodologies




‘a methodology is a collection of procedures, techniques, tools and documentation aids, supported by a philosophy, which will help the systems developers in their efforts to implement a new information system’

(Avison & Fitzgerald)

‘a set of principles of method, which in any particular situation has to be reduced to a method uniquely suited to that particular situation’

(Checkland)



Levels of abstraction

Increasing level ofabstraction

Example of application Typical product

Task Developing a first-cut class diagram forFoodCo.

A specific version ofthe FoodCo classdiagram.

Technique Description of how to carry out atechnique, e.g. UML class modelling.

Any UML classdiagram.

Method Specific techniques used on a particularproject (e.g. FoodCo use cases, classmodel, collaboration diagrams, etc.) thatlead to a specific product.

FoodCo’s productcosting system.

Methodology General selection and sequence oftechniques capable of producing a rangeof software products.

A range of object-oriented businessapplications.

Bennett, McRobb, Farmer 1999



Systems Development Methodologies A methodology comprises:

– Phases & Sub-phases– Techniques & Tools– Guidance on how to use the techniques &

tools at each stage within a phase or sub-phase

– Specified deliverables– How the project will be management– An all encompassing philosophy




Survey of software developers across Europe :

-



Why use a methodology? Better systems Use of a methodology better than none

at all Aim to improve



Objectives

Objectives of a methodology:




The techniques need to possess:

– notational accuracy

– notational simplicity

– an appropriate semantic

Use of a methodology still does not solve all the problems of system development



Systems Development Methodologies User training necessary

Commercially packaged products usually include:-

- manuals

- education and training

- consultancy support

- automated tools

- pro forma documents

- model building templates



Benefits of Methodological Approach Standardised process Benefits



Benefits

Produce a better quality product:

Help to ensure user requirements are met completely.



Benefits

Helps the project manager, by giving

Promote communication between project participants by



Limitations

Methodologies vary widely e.g.

No guarantee of success Quality of developers most

important Methodological fashion changes !



Limitations Applicability of methodology depends on

– type of application– size of system– complexity– technology being used– experience & training of developers– and other factors …

It is important to choose a suitable methodology



Different Perspectives

Methodologies differ in



Unified Process

Unified Process has four phases

– Inception– Elaboration– Construction– Transition

It uses UML



Unified Process

What are its workflows:



DSDM Dynamic Systems Development Method

Suggests a slightly different view of the lifecycle than UP

Fundamentally iterative



DSDM

Functional model iteration

Feasibility

Business study

Design and build iteration

Implementation

Forward paths through process

Backward paths to evolve the

system



SSADM

Structured Systems Analysis and Design Method - version 1 launched in 1981

Developed, funded and controlled by CCTA

Version 4+ produced in 1995 -96 Latest version is 4.3

CCTA = Central Computing and Telecommunications Agency



SSADM

Comprises: Uses traditional techniques - DFD, E-R

etc.



Yourdon

Developed during 70’s & 80’s– Many contributors including Ed Yourdon

Structured, various flavours including real-time.

Uses similar techniques to SSADM



Real-Time Yourdon

Methodology developed from work of– De Marco– Constantine & Yourdon– Chen & Flavin– MacMenamin & Palmer

Developed by– Ward & Mellor– Hatley & Pirbhai



Real-Time Yourdon The methodology comprises

– Essential Model

– Implementation Model



Real-Time Yourdon

Structured Analysis & Design is based upon 3 perspectives



Summary

Explain what is meant by methodology Examine benefits and limitations Consider alternative views of lifecycles A brief review of exemplar

methodologies



References Bennett, S., McRobb, S. & Farmer, R. Object-

Oriented Systems Analysis and Design using UML McGraw-Hill 2002, (Ch 22)

Jacobson, I., Booch, G. and Rumbaugh, J. (1999), The Unified Software Development Process, Addison-Wesley, Reading Mass. (Ch 7)

Rational Unified Process 2000

Avison, D.E., Fitzgerald, G. (1995) Information Systems Development: methodologies, techniques and tools, 2nd. Ed. McGraw-Hill

Documents

Requirements Analysis 18. 1 SDM - 2005b518.ppt © Copyright De Montfort University 2000 All Rights Reserved INFO2005 Requirements Analysis Systems Development