Software Production and Lifecycle Models

ICS 121

and Lifecycle Models

– Personnel

– Basic Phases

– Potential Difficulties

– Validation, Verification, and

Testing Problem Definition Validation Requirements Change Validation Operation Revalidation Requirements Specification Validation Architectural Design Specification Verification Implementation and Integration Testing

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Problems: Essence and Accidents

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Software is conceptual (intangible)

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Essence: difficulties inherent in the intrinsic nature of

software

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Accidents: difficulties encountered today, but not

inherent in software production

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Accidents are amenable to research breakthroughs

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Essence constitutes those problems that are unsolvable

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Software Production Personnel

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Client – individual or organization that want product to

be developed

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Developer(s) – (members of) organization producing

product

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User – person on whose behalf client has commissioned

developer, person(s) who will utilize software in

operation

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internal software development: client = developer

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THROUGH PROCESS

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Quality Software Products developed through

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Effective testing and analysis must be included

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Powerful tools and processes are essential to

assure effectiveness

• Process Models

• Processes

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What is a Process?

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Device for producing a product (getting job done)

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Indirect nature

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instances

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Humans create process descriptions (models or

programs) to solve classes of problems

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Software Processes:

devices for creating and evolving software

products

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The Lifecycle Approach

Major Components of a Lifecycle Model:

• Phases

• Reviews

• Intermediate Products

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Phasing promotes manageability and provides

organization

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Reviews assure ultimate satisfaction of requirements

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Intermediate products promote visibility and assure

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Intermediate Software Products

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Objectives:

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Form:

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Content:

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Phases of a SW Lifecycle Model

Requirements Change Validation Operation and Revalidation Validation Verification Implementation and Integration Testing Requirements Analysis + Specification Design Maintenance

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Requirements Analysis and Specification

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Problem Definition —> Requirements Specification

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constraints

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Difficulties

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Validation

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specification satisfies client needs

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Design

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Requirements Specification —> Design

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software into modules with module interfaces

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and data structures

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Difficulties

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Verification

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determine that design conforms to requirements

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Implementation and Integration

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Design —> Implementation

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Difficulties

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productivity

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Verification and Testing

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that implementation conforms to requirements and design

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module functionality

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ICS 121

Operation and Maintenance

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Operation —> Change

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Difficulties

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Verification and Testing

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all documentation updated

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compromise system functionality (check that no affected software has regressed)

ICS 121

Lifecycle Models

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Over time different lifecycle models were developed, e.g.,

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Different lifecycle models decompose software

engineering activities in different ways

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Build and Fix Approach

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client feels software can be used productively

O pe ra tion B u ild Firs t Ve rsion D e velo pm e nt M a int en an c e I nt erm e dia te P ro du ct M od ified P ro du ct (un til c lie nt is sat isf ie d )

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Stagewise Development

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P ro ble m De fin it io n Va lida tio n I nt eg ra tion I nt eg ra tio n a nd S y s t em Te s tin g R e qu ire m e nt s C h an ge Valida tio n P h a ses O p e rat io n Re va lid at io n D e tailed D e s ig n S p e cific a tion Ve rificat io n Re qu irem e n ts Sp e cif ic a tio n Va lid a tion A rc h it ectu ra l De s ign S p ec ific at io n

Ve rif ica tio n

Im p lem e n ta tion U nit/ M od u le Te s ting M a int en a nc e Re vie w s In term e d ia te P rod uct V & V S o ft wa re De ve lo p m en t

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Waterfall Model [Royce,1970]

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Pro ble m Defin it io n

Va lidatio n I nt eg ration I nt eg ra tion a nd S yst em Testin g R e qu ire m e nt s C h an ge Validatio n Ph a ses Op e rat io n Re va lid at io n D e taile d D e sig n S p ecif ication Ve rificat io n Re qu irem en ts

Spe cif ica tio n

Va lida tion

Arch it ect ura l De sign Sp ecifica tio n

Ve rif ica tio n

I m ple me n ta tion

U nit/ Mod ule Te sting Maint en a nce Review s In term ed iat e P rod u ct V& V Sof tw are D eve lop m e nt

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Test Development

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P ro ble m De fin it io n Va lid at io n In te gra tion I nt eg ra tion a nd S y s t em Tes tin g O p e rat io n R ev a lid at io n D e ta ile d D e s ig n S p e c if ic a tio n V erific at io n Re q uire m en ts S pe c ific at io n Valida tio n A rc h it ec t ura l De s ign S p ec ific a tion Ve rifica tio n U n it Te s t P lan In te g ratio n Te s t P la n S y s tem / A c c e pta n c e Te s t P la n M o du le I nt erf ac e Te st P lan Re v iew s In te rm ed ia te P rod u ct V erific at io n S o ft wa re D eve lo p m en t Tes t D ev e lo p m en t Te s t P lan Tes t Us e I m ple m en ta tion U nit/ M od u le Te s ting

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Exploratory Programming

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build system and expose to user review, modify system until performance is adequate Build Software System O peration Development Maintenance Intermediate Product Develop Outline Specificaiton U se

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Prototyping Model

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follow traditional lifecycle (could also have feedback)

R ap id Pro totype Va lid at ion In te gra tion I nt eg ra tion a nd Syst em Testing R e qu irem e n ts C h an g e Va lida tion D e tailed D e sig n S p ecif ica tion

Verificat ion Re q uire m en ts

Spe cificat io n

Valida tio n

Archit ect ura l De sign Sp ecification

Ve rifica tio n

I m ple men ta tion

U nit/ M odu le Te sting Ma int en a nce Review s In te rm ediat e P rod u ct V &V S of twa re D eve lop m e nt

Op e rat io n

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Evolutionary/Incremental Model

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operational product until complete, direction of evolution determined by operational experience (development process should use waterfall

model) O p era tion D e v e lo p F i r s t B u i ld Te s t I n t e g r a te a n d Te s t D e v e l o p m e n t M a i n t e n a n c e I n t e r m e d ia te P r o d u c t Develop Increment

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Transformation Model

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correctness-preserving transformations

Pro ble m De fin it io n

Validatio n In te gratio n Te sting R equ ireme n ts C han ge Va lidatio n Transfo rm ation a nd Op timizat io n Ve rif icatio n F orm al Spe cification Ve rificat ion R e qu irem ents

Specif ica tion

Va lid at io n

Op erat io n

R eva lid at ion M a int en a nce

In term ed iat e Prod uct

Sof tware D eve lop me nt

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Simplistic View of Spiral Model

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Opera tion Re validat io n R isk Analysis R e qu iremen ts Specificat io n Validation Verification D esign Specificat io n R isk Ana lysis Ra pid

Prot otype Validation R isk Ana lysis

Imp leme ntation and I ntegrat ion

Testin g R isk Analysis

Maint enance Soft ware Develop men t

Interme diate Product V&V R isk Analysis R eviews R isk Analysis R e qu iremen ts Ch ange Valida tion

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The Spiral Model [Boehm,1988]

Concept of Operation Requirements Plan Requirements OAC Risk Assessment

Risk Item Set

Risk Management Plan

Requirements Risk Control Requirements Validation Abstract Specification Plan Abstract Specifcation OAC Risk Assessment Risk Control Abstract Specification Abstract Specification Validation Concrete Specification Plan Concrete Specification OAC Concrete Specification Concrete Specification Validation and Verification Software Development Plan Risk Assessment Risk Control Progress through steps Cumulative cost Evaluate alternatives, identify, resolve risks

Develop, verify next-level product Plan next phases

Commit Review partition Determine objectives, alternatives, constraints (OAC)

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Capability Maturity Model (CMM)

[Watts Humphrey,1989]

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CMM is not a software lifecycle model

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Strategy for improving the software process regardless

of the process model followed

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productivity and quality, but rather software management is in part the cause of problems

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achieving a disciplined and mature process

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Includes both,

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Capability Maturity Model - 2

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Five maturity levels

1. initial – ad hoc process

2. repeatable process – basic project management 3. defined process – process modeling and definition 4. managed process – process measurement

5. optimizing process – process control and dynamic improvement

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to aid in maturation, the SEI has a series of

questionnaires and conducts process assessments that

highlight current shortcomings

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ISO 9000

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Further attempt to improve software quality based on

International Standards Organization (ISO)

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ISO 9000 = series of five related standards

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software development

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Basic features:

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Adopted by over 60 countries (e.g., USA, Japan,

European Union, ...)

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Company needs to be certified that its process complies

ICS 121

ICS 121 Lifecycle Model