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The Waterfall Lifecycle Approach

Thoroughly clarify, record, or implement each phase of the projectbefore beginning the next. The subsequent phase is based upon thedesign documentation previously developed.

Requirements

Analysis

Design

Implementation

Integration and Testing

Maintenance

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The Waterfall Lifecycle Approach

Problems with the Waterfall Approach

Large steps are taken in which many decisions are made withoutthe benefit of feedback.

Requirements and Design decisions, once established, are frozen inplace.

High risk or difficult problems are tackled late.

Speculative decisions increase and compound.

There is low adaptability for incorporating either design or

implementation concepts learned in the development processinto the project.

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The Unified Process

The Unified Process is a software development process ormethodology that above all promotes Iterative Development.

The result of each iteration is an executable, but incompletesystem. The system may need many iterations before it is

ready for production.

Benefits of iterative development include:

Early mitigation of high risksEarly visible progress.

Early feedback, user engagement, and adaptation, leadingto a system that more nearly meets the needs of the variousstakeholders.Managed complexity no compounding of complexity bypostponing the implementation phase.

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Supports System Development Using the UnifiedModel Language (UML)

Evolutionary process where the system is builtiteratively and incrementally in several buildsstarting from the requirements phase

Architecture-centric

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RUP is a complete software-development processframework , developed by Rational Corporation.

Its an iterative development methodology basedupon six industry-proven best practices.

Processes derived from RUP vary from lightweightaddressing the needs of small projects to morecomprehensive processes addressing the needs of

large, possibly distributed project teams.

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RUP is divided into four phases, named:

Inception

Elaboration Construction

Transition

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The Unified Process

Inc. Elaboration Construction Trans.

phase phase

iteration

Final releaseRelease

The end of each

iteration is aminor release

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The Unified Process

Inception: Define the scope of the system (identify all externalentities with which the system will interact and define thenature of the interactions)

Elaboration: Specify features and develop the architecture

Construction: Build the system

Transition: Transition Product to its users

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Inception

The life-cycle objectives of the project are stated,so that the needs of every stakeholder areconsidered. Scope and boundary conditions,

acceptance criteria and some requirements areestablished.

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Inception - Activities

Formulate the scope of the project.

Needs of every stakeholder, scope, boundaryconditions and acceptance criteria established.

Plan and prepare the business case. Define risk mitigation strategy, develop an initial

project plan and identify known cost, schedule, andprofitability trade-offs.

Synthesize candidate architecture.

Candidate architecture is picked from variouspotential architectures

Prepare the project environment.

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Inception - Exit criteria

An initial business case containing at least a clear

formulation of the product vision - the core requirements- in terms of functionality, scope, performance, capacity,

technology base. Success criteria (example: revenue projection).

An initial risk assessment.

An estimate of the resources required to complete the

elaboration phase.

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An analysis is done to determine the risks, stability ofvision of what the product is to become, stability ofarchitecture and expenditure of resources.

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The products and artifacts described in the exitcriteria of the previous phase.

The plan approved by the project management,and funding authority, and the resources required

for the elaboration phase have been allocated.

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Define the architecture.

Project plan is defined. The process,infrastructure and development environment are

described. Validate the architecture.

Baseline the architecture.

To provide a stable basis for the bulk of the

design and implementation effort in theconstruction phase.

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A detailed software development plan, with anupdated risk assessment, a management plan, astaffing plan, a phase plan showing the number and

contents of the iteration , an iteration plan, and atest plan

The development environment and other tools

A baseline vision, in the form of a set of evaluationcriteria for the final product

A domain analysis model, sufficient to be able tocall the corresponding architecture complete.

An executable architecture baseline.

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The Construction phase is a manufacturingprocess. It emphasizes managing resources andcontrolling operations to optimize costs, schedules

and quality. This phase is broken into severaliterations.

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The product and artifacts of the previous iteration.The iteration plan must state the iteration specificgoals

Risks being mitigated during this iteration.

Defects being fixed during the iteration.

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Develop and test components.

Components required satisfying the use cases,scenarios, and other functionality for the iteration

are built. Unit and integration tests are done onComponents.

Manage resources and control process.

Assess the iteration

Satisfaction of the goal of iteration isdetermined.

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The same products and artifacts, updated, plus:

A release description document, which captures theresults of an iteration

Test cases and results of the tests conducted on theproducts,

An iteration plan, detailing the next iteration

Objective measurable evaluation criteria for assessingthe results of the next iteration(s).

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The transition phase is the phase where theproduct is put in the hands of its end users. Itinvolves issues of marketing, packaging, installing,

configuring, supporting the user-community,making corrections, etc.

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The product and artifacts of the previous iteration,and in particular a software product sufficientlymature to be put into the hands of its users.

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The RUP puts an emphasis on addressing very earlyhigh risks areas.

It does not assume a fixed set of firm requirements

at the inception of the project, but allows to refinethe requirements as the project evolves.

It does not put either a strong focus on documents

The main focus remains the software product itself,and its quality.

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RUP is not considered particularly agile However,recent studies have shown that by adopting theright essential artifacts RUP is agile.

It fails to provide any clear implementationguidelines.

RUP leaves the tailoring to the user entirely.

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Management of a Software

ProjectThere are two groups involved with the management of a softwareproject:

Management whose concern is resource allocation, deliverydates, profit margin, etc.

Technical staff whose concern is producing a well-engineered

product within the constraints of the project.

Management likes benchmarks exemplified in the Waterfallapproach. Due dates can be set, and resources allocated to each

phase of the project, and project management documents can be

completed according to a schedule.

The iterative process as emphasized in UP is a better approach for

engineering a software product, but it less suited for producing project reports

that indicate the status of the project and the completion of well-definedphases of the work important to management.

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The emphasis is on finding and describing theobjects (or concepts) in the problem domain.

In a Library Information System, some of theconcepts include Book, Library, and Patron.

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Object Oriented Analysis

OOAOOA Develops a Logical Model of the system as aset of interacting domain objects

The model consists of two views

The static view: defines the classes

and their dependencies

The dynamic view: models the scenarios ofinteractions between objects

Class AClass B

Requires

Service

FromClass B

Obj s:Class A

Obj y:Class B

3: Set_Alarm(message)

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The emphasis is defining software objects and howthey collaborate to fulfill the requirements.

In a Library Information System, a Book softwareobject may have a title attribute and a get

Chaptermethod.

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During Implementation, orObject-OrientedProgramming, design objects are implemented,such as a book class in Java.

Implementation is also known as Coding or

Construction.

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UML stands for Unified Modeling Language

The UML is the standard language for visualizing,specifying, constructing, and documenting theartifacts of a software-intensive system

It can be used with all processes, throughout thedevelopment life cycle, and across differentimplementation technologies.

The Unified Modeling Language

UML

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The UML may be used to:

Develop a Requirements Model1. Use Case diagrams - Define the scope, and

display the boundary of a system & its major

functions using use cases and actors2. System Sequence diagrams - Illustrate use case

realizations or scenarios of interactionsbetween the actors and the system

Develop the Analysis model

1. Class diagrams - Represent a static structure ofa system

2. State Charts - Model the behavior of objects

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Develop the architecture design model

1. Class diagrams: Represent the staticarchitecture using packages or subsystems

2. Design Sequence diagrams: Represent thedynamic interactions between the designobjects

Develop the physical architectureimplementation model

1. component & deployment diagrams: Revealthe physical implementation architecture

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UML Development - Overview

PROGRAM

ACTORS

ANALYSISSpecify Domain

Objects

Detailed DESIGN

IMPLEMENTATION

D

A

T

A

DI

C

T

I

O

N

AR

Y

TimeUSE CASES

ANALYSISCLASS DIAGRAM(S)

IMPLEMENTATION

Activity DIAGRAMS

System/ObjectSEQUENCE

DIAGRAMS

OPERATIONCONTRACTS

StateChartDIAGRAMs

DEPLOYMENT DIAGRAMSUBSYSTEM CLASS/OR COMPONENT

DIAGRAMS

ArchitecturalDesignIncludeDesign Objects

ObjectDesign

SCENARIOS

REQUIREMENTSELICITATION

DESIGN DIAGRAMS

IMPLEMENTATIONCHOICES

DESIGN SEQUENCE DIAG.

Requirements

Engineering

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UML Diagrams

Structural diagrams Used to describe thebuilding blocks of the system features that do

not change with time. These diagrams answerthe question What's there?Behavioral diagrams Used to show how thesystem evolves over time (responds to requests,

events, etc.)

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UML Diagrams

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UML Diagrams

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