Clarke, R.J. (2000) EDM-DSL 1 EDM. Clarke, R.J. (2000) EDM-DSL 2 ESD Related Definitions (1) Evolutionary Systems Development (ESD)- is the formal name

Clarke, R.J. (2000) EDM-DSL 1

EDMEDM


ESD Related Definitions ESD Related Definitions (1)(1)

Evolutionary Systems Development (ESD)- is the formal name for Evolutionary Prototyping

An approach whereby the initial design proposals are put forward in the form of a physical working model

Analysts, working in partnership with users, gradually improve the prototype of the system...

...until it meets a level of acceptability decided by the user.

When this happens the prototype becomes the new system


ESD Related Definitions ESD Related Definitions (2)(2)

Evolutionary Prototyping (EP)Evolutionary Prototyping (EP) is the is the general namegeneral name for the activity developers for the activity developers undertake when they are involved in undertake when they are involved in Evolutionary Systems DevelopmentEvolutionary Systems Development

Evolutionary Development Methodology Evolutionary Development Methodology (EDM)(EDM)- a methodology which supports - a methodology which supports ESDESD


EDLCEDLC


RPLC RPLC

Investigation

Construction

Analysis

Design

40-40

DevelopPrototype

TestPrototype

AmendPrototype

Maintenance &Evaluation

Operation &Acceptance


EDLCEDLC

DevelopPrototype

TestPrototype

AmendPrototype


Evolutionary Development Evolutionary Development (1)(1)

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

TestPrototype

AmendPrototype

CandidatePrototypes

DevelopPrototype

DevelopPrototype



DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

AmendPrototype

Spawn

TestPrototype



TestPrototype

AmendPrototype

DevelopPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

SpawnTest

Prototype

DevelopPrototype

AmendPrototype



TestPrototype

AmendPrototype

DevelopPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

DevelopPrototype

TestPrototype

AmendPrototype

TestPrototype

DevelopPrototype

AmendPrototype

AmendPrototype



TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

DevelopPrototype

TestPrototype

TestPrototype

AmendPrototype

TestPrototype

AmendPrototype

DevelopPrototype

Merge

DevelopPrototype

DevelopPrototype

AmendPrototype

AmendPrototype



TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype

TestPrototype

AmendPrototype

DevelopPrototype


Prototype ClassificationPrototype Classification


Prototype ClassificationsPrototype Classifications

Several classifications exist for Several classifications exist for distinguish the function or distinguish the function or purpose of a prototypepurpose of a prototypeFloyd (1984)Floyd (1984)Law (1985)Law (1985)Mayhew & Dearnley (1987)Mayhew & Dearnley (1987)


Prototype ClassificationsPrototype ClassificationsFloyd’s ClassificationFloyd’s Classification

distinguishes three broad distinguishes three broad approaches to prototypingapproaches to prototypingexploratoryexploratoryexperimentalexperimentalevolutionaryevolutionary

structured the debate surrounding structured the debate surrounding prototyping in generalprototyping in general


Prototype ClassificationsPrototype ClassificationsFloyd’s Classification: Floyd’s Classification: ExploratoryExploratory

usefuluseful: early stages of systems : early stages of systems developmentdevelopment

focusfocus: communications problems : communications problems between prospective users and between prospective users and developersdevelopers

prototypeprototype: catalyst to participation : catalyst to participation and ideas generationand ideas generation

aimaim: assist in requirements gathering: assist in requirements gathering


Prototype ClassificationsPrototype ClassificationsFloyd’s Classification: Floyd’s Classification: ExperimentalExperimental

usefuluseful: testing all or some functions: testing all or some functions focusfocus: building a proposed solution : building a proposed solution

to a particular problemto a particular problem prototypeprototype: evaluated by : evaluated by

experimental use prior to eventual experimental use prior to eventual implementationimplementation

aimaim: reduce implementation costs: reduce implementation costs


Prototype ClassificationsPrototype ClassificationsFloyd’s Classification: Floyd’s Classification: Evolutionary Evolutionary (1)(1)

most controversial categorymost controversial category emphasis on gradual adaptation of emphasis on gradual adaptation of

the system in order to cope with the system in order to cope with changing organisational changing organisational circumstancescircumstances

system can be looked at as a system can be looked at as a sequence of sequence of versionsversions



each version once constructed, used each version once constructed, used and evaluated is and evaluated is treated as a treated as a prototypeprototype to its successor to its successorit has been argued that it should be called it has been argued that it should be called

‘versioning’‘versioning’but the use of a prototype means that it should but the use of a prototype means that it should

notnot be thought of as versioning! be thought of as versioning!



‘Version’ 1

?

?

‘Version’ 2



‘Version’ 2

?

? ?

‘Version’ 3



?

? ?

‘Version’ 3 Final ‘Version’

A

B

C


Prototype ClassificationsPrototype ClassificationsImportance of Floyd (1984)Importance of Floyd (1984)

provoked developers into thinking about provoked developers into thinking about the the usesuses of prototypes of prototypes

typical questions included:typical questions included:aim of building the prototype?aim of building the prototype?which category?which category?appropriateness of particular types of prototypes at appropriateness of particular types of prototypes at

certain stages in the systems development?certain stages in the systems development?improving the development by using a different improving the development by using a different

series of prototypes?series of prototypes?


Prototype ClassificationPrototype ClassificationLaw’s Types Law’s Types (1)(1)

developed an extended (5) developed an extended (5) classification of prototypesclassification of prototypes

distinction between types is not distinction between types is not absoluteabsolute

relates to the chief purpose of a relates to the chief purpose of a prototype in relation to its prototype in relation to its typical typical occurenceoccurence (timing) during the (timing) during the development processdevelopment process



ExploratoryExploratoryassist in the clarification of requirementsassist in the clarification of requirementsprototyping the prototyping the logical specificationlogical specificationas per Floydas per Floyd

ExperimentalExperimentalto find the solution to a particular problemto find the solution to a particular problemprototyping the prototyping the designdesignas per Floydas per Floyd



PerformancePerformancecheck whether solution handles workloadcheck whether solution handles workloadsyntheticsynthetic prototyping- prototype is run prototyping- prototype is run

through a simulated workloadthrough a simulated workloadnecessary simplification of the prototype necessary simplification of the prototype

makes this difficultmakes this difficultnevertheless, useful for identifying nevertheless, useful for identifying

incompatible combinations of problem, incompatible combinations of problem, hardware, software, peoplehardware, software, people



OrganisationalOrganisationala a special casespecial case of experimental prototyping used to of experimental prototyping used to

test a solution in proposed user environmenttest a solution in proposed user environmentascertain that a users requirements are metascertain that a users requirements are metclarify the needs of the surrounding organisationclarify the needs of the surrounding organisationneeds may be met by changing manual procedures, needs may be met by changing manual procedures,

staff, equipment, job descriptions, trainingstaff, equipment, job descriptions, training



EvolutionaryEvolutionaryrefers to the situation that exists when the refers to the situation that exists when the

prototype is in operationprototype is in operationthrough its use necessary alterations become through its use necessary alterations become

apparentapparentwhen the need for change is recognised the when the need for change is recognised the

operational system (‘version’) becomes the operational system (‘version’) becomes the prototype for the development of an enhanced prototype for the development of an enhanced systemsystem

as per Floydas per Floyd


Prototype ClassificationPrototype ClassificationImportance of Law’s TypesImportance of Law’s Types

like Floyd tries to provide a like Floyd tries to provide a functional description of different functional description of different types of prototypestypes of prototypes

unlike Floyd, tries to describe unlike Floyd, tries to describe most possibilitiesmost possibilities

provides an appreciation of the provides an appreciation of the scope of prototypingscope of prototyping


Prototype ClassificationPrototype ClassificationPUSH Model: Mayhew & Dearnley PUSH Model: Mayhew & Dearnley (1)(1)

provide an alternative way of provide an alternative way of classifying prototypingclassifying prototyping

based on the central ‘participants’ based on the central ‘participants’ found in any prototyping situationfound in any prototyping situationPrototyper (P)Prototyper (P)User (U)User (U)Software (S)Software (S)Hardware (H)Hardware (H)



each ‘participant’ (corner) interacts each ‘participant’ (corner) interacts with all the otherswith all the others

can draw the interactions using a can draw the interactions using a pyramid (edges)pyramid (edges)

can recognise each of Law’s types of can recognise each of Law’s types of prototypes accordingly- with some prototypes accordingly- with some interesting results! interesting results!



Software

Users Hardware

Prototype


Prototype ClassificationPrototype ClassificationPUSH Model: PUSH Model: Exploratory PrototypingExploratory Prototyping (4)(4)

prototyping the specificationprototyping the specification centres on communicationcentres on communication involves P, U, Sinvolves P, U, S Software

Users Hardware

Prototype


Prototype ClassificationPrototype ClassificationPUSH Model: PUSH Model: Experimental PrototypingExperimental Prototyping (5)(5)

adequacy of proposed solutionadequacy of proposed solution involves P, S, Hinvolves P, S, H 3 subtypes:3 subtypes:

experimentalexperimental prototyping prototypingPSPS

Software

Users Hardware

Prototype




performanceperformance prototyping prototypingSHSH

Software

Users Hardware

Prototype




hardwarehardware prototyping prototypingPHPH

Software

Users Hardware

Prototype


Prototype ClassificationPrototype ClassificationPUSH Model: PUSH Model: Organisational PrototypingOrganisational Prototyping (8)(8)

clarify wider system requirementsclarify wider system requirements involves U, S, Hinvolves U, S, H 3 subtypes:3 subtypes:

ergonomicergonomic prototyping prototypingUHUH

Software

Users Hardware

Prototype


Prototype ClassificationPrototype ClassificationPUSH Model: PUSH Model: Organisational PrototypingOrganisational Prototyping (9)(9)

clarify wider system requirementsclarify wider system requirements involves U, S, Hinvolves U, S, H 3 subtypes:3 subtypes:

functional functional prototypingprototypingUSUS

Software

Users Hardware

Prototype


Prototype ClassificationPrototype ClassificationPUSH Model: PUSH Model: Evolutionary PrototypingEvolutionary Prototyping (10)(10)

but, cannot fit but, cannot fit evolutionary evolutionary prototypingprototyping onto the picture onto the picture

Mayhew and Dearnley argue that Mayhew and Dearnley argue that evolutionary prototyping has h/w and evolutionary prototyping has h/w and s/w implications, therefores/w implications, thereforeevolutionary prototyping is simply an extension evolutionary prototyping is simply an extension

of organisational prototyping of organisational prototyping evolutionary prototyping simply has a longer evolutionary prototyping simply has a longer

time lapse between enhancementstime lapse between enhancements



S

UH

P HardwareExploratory

Experimental

PerformanceErgonomic

Functional


Characteristics of ESDCharacteristics of ESD


Characteristics of ESD Characteristics of ESD (1)(1)

OverlapOverlap of Analysis, Design and of Analysis, Design and Construction StagesConstruction Stages

Limited ModellingLimited Modelling of the Existing System of the Existing System emphasis on emphasis on early identification of the early identification of the

'logical' requirements'logical' requirements, so that quick , so that quick prototypes can be producedprototypes can be produced



PartnershipPartnership and User Responsibility and User Responsibility both analysts and users bring both analysts and users bring

unique expertiseunique expertise FormalisationFormalisation of Prototype of Prototype

BoundariesBoundaries system development can consist of system development can consist of

many small prototypes, many small prototypes, need to need to delineate each prototypedelineate each prototype



Early ImplementationEarly Implementation Flexibility & ScalabilityFlexibility & Scalability- tailor the - tailor the

methodology to the needs of methodology to the needs of organisationorganisation



in in RPRP, the purpose of the prototype , the purpose of the prototype was only to was only to gather requirementsgather requirements during analysis and designduring analysis and design

in in ESDESD, the main purpose of the , the main purpose of the prototype is to promote prototype is to promote communicationcommunication

the prototype serves the prototype serves manymany purposes often simultaneouslypurposes often simultaneously


Benefits of ESDBenefits of ESD


Benefits of ESD Benefits of ESD (1)(1)

Involving, committing and satisfying usersInvolving, committing and satisfying users Decreasing communications problemsDecreasing communications problems Decreasing development costsDecreasing development costs Reducing operational costsReducing operational costs Reducing time for developmentReducing time for development Producing the right system first timeProducing the right system first time Cutting human resource requirements during Cutting human resource requirements during

developmentdevelopment


Benefits of ESD Benefits of ESD (2)(2)

Stage Overlap or more correctly Stage Overlap or more correctly Partial Stage OverlapPartial Stage Overlap

Incremental DeliveryIncremental Delivery Tailorability of EDMsTailorability of EDMs User ParticipationUser Participation

we will concentrate on the first two we will concentrate on the first two benefits, in a following lecture we will benefits, in a following lecture we will discuss the last twodiscuss the last two


Partial Stage OverlapPartial Stage OverlapEDMEDM


Partial Stage Overlap (1)Traditional Development (SDLC)

Feasibility

StudyCurrentSystem

DefineRequirements

DesignNew System

Program

Test

Acceptance TrainUsers

Convert Install

Does not support Stage Overlap


Partial Stage Overlap (2)EDM

Feasibility

StudyCurrentSystem

DefinePrototype

DevelopPrototype

TestPrototype

Convert Install



DevelopPrototype

TestPrototype

Convert Install

Feasibility

StudyCurrentSystem

DefinePrototype



DevelopPrototype

Feasibility

StudyCurrentSystem

DefinePrototype

TestPrototype

Convert Install



Feasibility

StudyCurrentSystem

Convert Install



Feasibility

StudyCurrentSystem

Convert Install



Convert Install

Feasibility

StudyCurrentSystem



Supports Partial Overlap

Feasibility

StudyCurrentSystem

Define Prototype

Develop Prototype

Test Prototype

Convert Install


Stage Overlap Comparison (4)SDLC and EDLC Based Methodologies

DefineDevelop

TestFinish

Prototyping

FinishProject

StartProject


Incremental DeliveryIncremental Delivery



A

B

C



A

B

C

A B C Sta Fin Sta Fin Sta Fin

t0 1:4 1

t1 1:4 1

t2 2 2,3

t3 1 2 2,3

t4 1



A

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t0 1:4 1

t1 1:4 1

t2 2 2,3

t3 1 2 2,3

t4 1



A

B

C


t0 1:4 1

t1 1:4 1

t2 2 2,3

t3 1 2 2,3

t4 1



A

B

C


t0 1:4 1

t1 1:4 1

t2 2 2,3

t3 1 2 2,3

t4 1



A

B

C


t0 1:4 1

t1 1:4 1

t2 2 2,3

t3 1 2 2,3

t4 1

Documents

Clarke, R.J. (2000) EDM-DSL 1 EDM. Clarke, R.J. (2000) EDM-DSL 2 ESD Related Definitions (1) Evolutionary Systems Development (ESD)- is the formal name