Acca 11(information systemsdevelopmentprocess)

1

Information Systems Development Process

Lecture 11

Abdisalam Issa-SalweFaculty of Professional Studies

Thames Valley University

Abdisalam Issa-Salwe, Thames Valley University2

Topic list

System development lifecycle The Waterfall Model The Spiral Model Systems development

methodologies Software support for the systems

development process User involvement


System development cycle

In early days of computing, systems were developed in fairly haphazard way resulting in poorly designed systems which were too expensive and were not suited to the user’s needs

In the 1960s, the National Computing Centre developed a more disciplined approach to systems development which was applicable almost everywhere


System development cycle (cont…)

This approach was called the Systems Development Lifecycle and contained the following stages:

Feasibility Study Systems Investigation Systems Analysis Systems Design Implementation Review and Maintenance



System development life-cycle was developed to add discipline to many organisations’ approach to systems development.

Systems development lifecycle is the process of conceiving, designing and implementing an information system.



The Systems Development Life Cycle (SDLC) is a framework for describing the phases involved in developing and maintaining information systems

Typical SDLC phases include planning, analysis, design, implementation, and support


Systems View

Systems approach emerged in 1950s more analytical approach to management &

problem solving Three parts:

Systems philosophy: View things as systems, interacting components working within an environment to fulfill some purpose

Systems analysis: problem-solving approach Systems management: Address business,

technological & organizational issues before making changes to systems


Drawbacks of the systems development

Insufficient emphasis on information needs

Sequential, inflexible approach Poor documentation Dissatisfied users Users’ requirements poorly defined


Drawbacks of the systems development (cont…)

As information systems grow in size and complexity, these problems may only get worse.

The best way to start approaching these problems is by studying them in more detail. Legacy Systems Increasing Systems Complexity Organisational Issues


The IS function has a poor reputation.

Despite huge investments in information technology: Systems development often takes more

time and resources than planned Information systems do not provide the

information needed or in the needed form

Information systems break down too often




Birrell and Ould [Birrell and Ould, 1985], describe the "b-Model“: The b-Model recognises that the

maintenance phase of the software life-cycle is seldom just fixing errors.

If a software product exists for any period of time, "maintenance" almost always involves enhancements.

After a while, the "maintenance phase" of a software product looks very much like the "development phase."


SSADM SSADM (Structured Systems Analysis

and Design)Originally designed for the UK Civil

Service.Data driven – concentration on the

data rather than processes. Highly structured with rules,

guidelines and standardsDocumentation is crucial to all

aspects of the system project development


SSADM states

Stage 0 – Feasibility Study Stage 1 – Investigation of Current

Environment Stage 2 - Business Systems Options Stage 3 – Definitions of requirements Stage 4 – Technical Systems Options Stage 5 – Logical Design Stage 6 – Physical Design


Computer-Aided Software Engineering Tools (CASE)

Software tools providing automated support for systems development

Project dictionary/workbook: system description and specifications

Diagramming tools Example products: Oracle Designer,

Rational Rose


CASE Tools (cont…)

Select - Select Visio 2000 – Microsoft Visible Analyst - Visible Systems ER/Studio - Embarcadero ERWin - Computer Associates Oracle Designer - Oracle Power Designer - Sybase


CASE Features

Diagrams Documentation Data Dictionary Team Coordination Prototyping Code Generation Reverse Engineering


CASE Types

Full development - integrated iCASE

Analysis & Design upper CASE

Implementation & Maintenance lower CASE


CASE Repository

Data dictionary - data element definitions and descriptions Ensures consistency

Repository is much more Database with linkages for all system

development products and activities Integration

Even across different CASE tools


System Development Methodologies

System Development Methodologies - Refer to tools and techniques used to complete tasks of various phases.We may use structured design

technique to design computer programs; the technique would be a methodology where as system design is a phase of the life cycle


System Development Methodologies (cont…)

A system development methodology is a guidelines to follow for completing every activity in the SDLC, including specific models, tools and techniques.

Some methodologies are very formal, and contain direct instruction. Everything is defined, including the view of documentation and content of reports.

Other methodologies are much more informal – just general description of what should be done.


System Development Methodologies (cont…)

Different types of system development methodologies are used in designing information system.

Depending upon the actual requirement of the system, different approaches for data processing are adopted. However, some system groups recommends the Centralised data processing system while others may go in for distributed data processing system.


Model

A model is a representation of some aspect of the real world. A model may be: physical (like a model of an airplane) or abstract (e.g. in form of mathematical notation

or in graphical form). Most models, used in system development, are

graphical (diagrams and charts). They include representations of inputs, outputs, processes, data, objects, object interactions, locations, networks, devices, or highlighting the tasks for the project


Tools A tool is a software support that helps

create models or other components required in the project. A list of tool types includes: Project management application Drawing/graphics application Word processor/text editor Computer-aided system engineering (CASE)

tools Integrated development environment (IDE) Database management application Reverse-engineering tool Code generator tool


Technique

A technique is a collection of guidelines that help the analyst complete a system development activity or task.

It might be step-by-step instructions or more general advices.


Technique (cont…) Strategic planning techniques Project management techniques User interviewing techniques Data-modeling techniques Relational database design techniques Structured analysis technique Structured programming technique Software-testing techniques (e.g. usability

testing) Object-oriented analysis and design

techniques



Computer Generation

First generation: machine language Second generation: assembly language Third generation: high-level

programming languages, such as C, C++, and Java.

Fourth Generation fifth generation: languages used for

artificial intelligence and neural networks.



Machine language (1GLs)

The lowest-level programming language (except for computers that utilise programmable microcode)

Machine languages are the only languages understood by computers.

While easily understood by computers, machine languages are almost impossible for humans to use because they consist entirely of numbers


Assembly language (2GLs) A programming language that is once

removed from a computer's machine language.

Machine languages consist entirely of numbers and are almost impossible for humans to read and write.

An assembly language contains the same instructions as a machine language, but the instructions and variables have names instead of being just numbers.


Fourth-Generation Languages (4GLs)

Often abbreviated 4GL, fourth-generation languages are programming languages closer to human languages than typical high-level programming languages. Most 4GLs are used to access databases. For example, a typical 4GL command is: FIND ALL RECORDS WHERE NAME IS

"SMITH"


5GLs

Fifth generation: languages used for artificial intelligence and neural networks.

the branch of computer science concerned with machine behave like humans. Example: Game playing Neutral network Robotics, Etc.


User involvement• User involvement focuses the

needs and wishes of users, i.e. crucial information that must be incorporated into the design process to ensure user acceptance.

• To begins by classifying the users of a product into several distinct user groups.

• Groups then examined using methods such as in-person interviews, group interviews.


User involvement

Walkthroughs: Walkthroughs investigate how a product is used in its actual usage environment and what are expectations and wishes of users concerning the product. In an unstructured walkthrough the user is allowed to freely demonstrate her way of using the product, while in a structured walkthrough the user is asked to perform specific tasks.

Acca 11(information systemsdevelopmentprocess)

Education

systems development

systems view systems

designed systems

systems philosophy

legacy systems

planned information

purpose systems analysis

development phase