systems development methodologies. what is a methodology? procedures + techniques + tools + phases =...

SYSTEMS DEVELOPMENT METHODOLOGIES

WHAT IS A METHODOLOGY?

Procedures +Techniques +

Tools +Phases = Method

Method + Philosophy = Methodology

WHAT IS A PHILOSOPHY?

e.g. building a system that:

- makes most use of computers or- is the cheapest to run or- is implemented earliest or- is the most adaptable or- is best liked by its users or

etc.

WHY USE A METHODOLOGY?

To introduce structure into design

To increase the likelihood of success

Previously:Problem - User - Programmer - Change

- Create Problem - User - Programmer etc

With Methodologies:Problem - Analysis - Design - Implementation - Success

EXAMPLES OF SYSTEMSDEVELOPMENT METHODOLOGIES

'Hard' MethodologiesSSADM (Structured Systems Analysis and Design Methodology)

STRADIS (Structured Analysis and Design)JSD (Jackson Structured Design)

'Soft' MethodologiesETHICS

SSM (Soft Systems Methodology)

Mix of 'hard' and 'soft'MULTIVIEW

SSADM (Structured Systems Analysis and Design Methodology)

Features:

Data DrivenDetailed rules

Comprehensive manuals

ForCovers all elements of life cycle

Used by Civil ServiceIt works!

AgainstOverkill for small projects

Stages

Analysis1. Analysis of Current System2. Specification of Required System3. Technical Options

Design4. Detailed Data Design5. Detailed Procedure Design6. Physical Design Control

1. Analysis of Current System

Identify bottlenecks/dissatisfactionUse interviews/questionnaires etc.Produce DFDs, LDSsAgree current system model with users

2. Specification of Required System

Expand current system to include new requirementsInclude data and process aspectsInclude audit, security and controlsProduce a consolidation of people's views

3. Technical Options

Centralised vs. DistributedOnLine vs. BatchResponse timesStaffing level implicationsOther resource implications

4. Detailed Data Design

Define data and data relationshipsEnsure data structure meets:Screen/Report requirementsProcessing requirements

5. Detailed Procedure Design

Catalog all functionsCheck against data structurePerhaps prototypeCheck logical design meets requirements

6. Physical Design Control

Produce plan for building/testing systemInclude program specs, operating procedures Consolidate documentation

STRADIS(Structured Analysis and Design)

Features:

Solution found from a number of possible modules and interfacesUses a selection of tools and techniques

ForSuited to any size system

AgainstMore about defining the solution than the problem

Stages

1. Initial Study2. Detailed Study3. Define and Design Alternative Solutions4. Physical Design

1. Initial Study

Aim to select systems which will:Reduce costsIncrease revenueImprove servicesSpeak to users and managersProduce overview DFDDecide whether to progress to next stage

2. Detailed Study

Identify users of new systemDraw level 1 DFDProduce lower levels of DFDProduce process descriptionsProduce detailed cost/benefit analysis

3. Define and Design Alternative Solutions

Convert organisational objectives intosystem objectives(i.e. make them specific, not general)

Produce level 1 DFD for new system

Produce three alternative solutions:

quick and cheap (some objectives met)longer and more costly (most met)longest and most expensive (all met)

4. Physical Design

Produce all logic and error handlingProduce data dictionaryProduce report and screen formatsProduce files/databaseIdentify clerical tasksAll down to a level where costs can be detailed

JSD(Jackson System Development)

Features:

Extension to JSP (Jackson Structured Programming)Transformation from program specification to implementation

ForModels a dynamic world

AgainstOrientated towards software rather than organisational needsSeveral elements of life cycle missinge.g.requirements analysisuser interfacedatabase design

Stages

Entity Action stepEntity Structure stepInitial Model stepFunction stepSystem Timing stepImplementation step

Entity Action stepDefine entities that perform or suffer actionse.g. customer, supplierbut by behaviour rather than relationshipTraditional entity modelling = staticJSD = dynamic

Entity Structure stepDraw diagrams to show life history(Boxes)Initial Model stepCreate model to simulate entity activity(Pseudo-code)Function stepAdd necessary functions to produce output(e.g. account balance)System Timing stepAdd delays to reflect real world(e.g. user requirements, technical restrictions)Implementation stepAllocate processors to processes

ETHICS (Effective Technical and Human Implementationof Computer-Based systems)

Features:

Adopts an ethical philosophyTechnology + Social + OrganisationalImproved job satisfaction and working lifeInvolves users in design decisions

ForWell accepted by users

AgainstTreated with suspicion by managementUsers may not have necessary skills

STAGES

Why ChangeSystem BoundariesDescription on Existing SystemDefinition of Key Objectives and TasksDiagnosis of Efficiency NeedsDiagnosis of Job Satisfaction NeedsFuture AnalysisSpecifying and Weighing Efficiency and Job Satisfaction Needs and ObjectivesOrganisational Design of the New SystemTechnical OptionsPreparation of A Detailed Work DesignImplementationEvaluation

Why ChangeAs the name implies, If not conclusive,then don't

System BoundariesConsider effect upon the following areas:Business ActivitiesExisting TechnologyParts of the OrganisationParts of the Organisation's environment

Description of Existing SystemIn terms of inputs, outputs and processes

Definition of Key Objectives and Tasks Roles, Purposes, Responsibilities and Functions

Diagnosis of Efficiency NeedsIdentify weak links

Diagnosis of Job Satisfaction NeedsStandard Questionnaire

Future AnalysisAllow flexibility for enhancements etc

Specifying and Weighing Efficiency andJob Satisfaction Needs and ObjectivesKey stepProduce objectives based on previous stepsRank these into primary and secondaryAll primary objectives must be metAs many as possible secondary should be met

Organisational Design of the New SystemIdentify operating activitiesIdentify coordination activitiesIdentify development activitiesIdentify control activitiesIdentify special skills requiredIdentify key roles or relationships

Technical OptionsEvaluate options for software, hardware, HCIin terms of efficiency, job satisfaction and future change.

The Preparation of a DetailedWork DesignDesign the system in detailIdentify data flows, tasks, groups etcEnsure objectives are still being met

ImplementationPlan implementation in detailStrategyEducation and TrainingCo-ordination

EvaluationCheck Objectives met

SSM (Soft Systems Methodology)

Philosophy:

A System is more than the sum of its partsModels of data and processes are simple,Involve people and they become ill-defined or 'fuzzy‘

ForDeals with the real world

AgainstToo much analysis, not enough design

Stages

Produce rich picture

Include clients, participants and tasks

Identify CATWOE:

C lient - beneficiary or victimA ctor - agent of changeT ransformation - the change taking placeW orld view (Weltanschauung) - assumptionsO wner - the sponsorE nvironment - the wider system

MULTIVIEW

FeaturesMix of hard and soft

ForBest of both worldsAgainst

Hotch-Potch of techniques

Stages

Analysis of human activity systemsLook at organisation, its purpose and problems

Information modellingAnalyse entities and functions

Analysis and design of the socio-technical systemConsider people, needs, working environment

Design of the Human-Computer InterfaceCommand, Form, Menu, Icon/Mouse, Natural Language?

Design of the technical sub-systemsCombine Entity model and Technical requirements

Outputs are:

Applications - processesInformation - producedDatabase - usedControl - error checkingRecovery - repairing mistakesMonitoring - keeping track for management