The Essence of Software Development Process

Software Development Process

Unit 1

12 marks

Definition of Software

Software is:

1. 

Instructions 

(computer programs) that when

executed provide desired features, function, and

performance;

2. 

Data structures 

that enable the programs to

adequately manipulate information, and

3. 

Descriptive information (documents) 

in both

hard copy and virtual forms that describes the

operation and use of the programs.

Characteristics of software

Software is developed or engineered; it is not

manufactured in the classical sense.

•

The two activities (software development and

hardware manufacturing) are fundamentally

different.

•

In both activities, high quality is achieved through

good design, but the manufacturing phase for

hardware can introduce quality problems.

•

Software doesn’t “wear out.” But it does

deteriorate!

•

During its life, software will undergo change. As

changes are made, it is likely that errors will be

introduced, causing the failure rate curve to spike

as shown in the “actual curve” .

•

Before the curve can return to the original

steady-state failure rate, another change is

requested, causing the curve to spike again.

•

Slowly, the minimum failure rate level begins to

rise—the software is deteriorating due to change.

Although the industry is moving toward component-

based construction, most software continues to

be custom built.

Categories of software /changing

nature of software

System software

 It is collection of programs written to service other programs.

Some system software (e.g., compilers,editors, and file management

utilities) processes complex, but determinate, information

structures.

 Other systems applications (e.g., operating system components,

drivers, networking software process largely indeterminate data.

Application software

 Stand-alone programs that solve a specific business need.

 Applications in this area process business or technical data in a

way that facilitates business operations or management/technical

decision making

Engineering/scientific software

 Applications range from astronomy to volcanology, from

automotive stress analysis to space shuttle orbital dynamics,

and from molecular biology to automated manufacturing

 E.g.: CAD software.

Embedded software

 Resides within a product or system and is used to

implement and control features and functions for the end

user and for the system itself.

 Embedded software can perform limited functions (e.g., key

pad control for a microwave oven) or provide significant

function and control capability (e.g., digital functions in an

automobile such as fuel control, dashboard displays, and

braking systems).

 E.g. Control buttons of washing machine.

Product-line software

 Designed to provide a specific capability for use by many

different customers.

 Product-line software can focus on a limited marketplace

(e.g., inventory control products) or address mass consumer

markets (e.g., word processing, spreadsheets, computer

graphics, multimedia,

entertainment, database management, and personal and

business financial applications).

Web applications

 Called “WebApps,” this network-centric software category

spans a wide array of applications.

 In their simplest form, WebApps can be little more than a

set of linked hypertext files that present information using

text and limited graphics.

Artificial intelligence software

 Makes use of non-numerical algorithms to

solve complex problems that are not amenable

to computation or straightforward analysis.

 Applications within this area include robotics,

expert systems, pattern recognition (image and

voice), artificial neural networks, theorem

proving, and game playing

Software Engineering:

A layered technology approach:

 Software engineering is a layered technology.

Referring to, any engineering approach (including

software engineering) must rest on an

organizational commitment to quality. The bedrock

that supports software engineering is a quality

focus.

 The foundation for software engineering is the

process layer. The software engineering process is

the glue that holds the technology layers together

and enables rational and timely development of

computer software. Process defines a framework

that must be established for effective delivery of

software engineering technology.

 The software process forms the basis for

management control of software projects and

establishes the context in which technical

methods are applied, work products (models,

documents, data, reports, forms, etc.) are

produced, milestones are established, quality is

ensured, and change is properly managed.

Software engineering methods provide the

technical how-to’s for building software.

 Software engineering tools provide automated

or semi-automated support for the process and

the methods. When tools are integrated so that

information created by one tool can be used by

another, a system for the support of software

development, called computer-aided software

engineering, is established.

The software process framework

/framework activities:

 A process framework establishes the 

foundation for a

complete software process

 by identifying a small number

of framework activities that are applicable to all software

projects, regardless of their size or complexity.

 In fig each framework activity is populated by a 

set of

software engineering actions

. A collection of related tasks

that produces a major software engineering work

product.

Each action in process framework is populated with

individual work tasks that accomplish some part of the

work implied by the action

1. Communication:

Communication framework activity involves heavy

communication and collaboration with the

customer, encompasses requirements gathering,

data gathering and other related activities.

2. Planning:

Planning activity establishes a plan for software

engineering work that follows. Planning describes

the technical tasks to be conducted, the resources

that will be required, schedule, and the risks that

are likely in the work products to be produced.

3. Modeling:

•

Modeling activity encompasses the creation of

models that allow the developer and the

customer to better understand software

requirements specifications and the design

that will achieve those requirements.

•

There are two types of modeling

  i.e. 

analysis modeling and design modeling

.

4. Construction:

Construction activity combines code generation

and the testing.

5. Deployment:

The software is delivered to the customers who

evaluates the delivered product and provides

feedback based on the evaluation.

Umbrella Activities:

•

Generic views of SE is complemented by a set of

unbrella activities.

•

They are Software Project tracking and control:



It allows the software team to 

access progress

against the project plan 

and takes necessary action

to maintain schedule.



Umbrella activities occur throughout the software

process and 

focus primarily on project

management, tracking and control

.

•

Risk Management

:

Assess risks that are likely to affect performance

and quality of project.

•

Software quality assurance

:

Define and conduct activities to ensure software

quality

•

Formal Technical Review: 

Assess Software Engg.

Work products to uncover and remove errors

before they are shifted to next level of activity.

•

Measurement: 

Defines and collects process,

project and product measures to assist the team

in delivering the software that meets customer

needs can be used in conjunction with all

framework and umbrella activities

•

Software configuration Management (SCM):

Manages and effects the changes throughout

the software process.

•

Reusability management: 

Defines criteria for

work product reuse (including software

components) and establishes the mechanism

to achieve reusable components.

•

Work product preparation and production:

Includes activities for creating work product

such as models, documents, large

Prescriptive Process Models:

Irrespective of which level of CMM the organization

has, the software engineer has five choices for

selection of software process models.

They are –

1. Waterfall Model

2. Incremental Model

3. RAD Model

4. Prototype Model

5. Spiral Model

The Waterfall Model:

 

Communication:

It involves heavy communication with the customer (or stakeholder) and encompasses

requirement gathering and related activities

.

 

Planning:

In this activity, 

effort required, cost/budget, risk analysis ,time duration

 are estimated

(project plan is made)

 

Modeling:

This activity 

creates analysis and design models 

that both developers and customer to

better understand the requirements. Data structure, software architecture and other

details are made.

 

Construction:

This activity performs 

code generation and testing 

to ensure whether requirements

are fulfilled.

Code generation is done first and then testing is done after that.

 

Deployment:

Once the product is fully developed, it is 

delivered to the customer

. Customer

evaluates the product and provides feedback.

•

one stage should be completed before the other

begins.

•

All phases are clearly defined.

•

Being oldest, this is one of the time tested Methods

•

Real projects rarely follow 

sequential model.

•

It is often difficult for the customer to state all

requirements explicitly.

•

The working model is available only in the latter part of

the development.

•

This model presents a 

high level view 

and

suggests to the developer the sequence of

events they should expect to encounter. This

model is 

used to prescribe software

development

 activities in variety of contexts.

•

One of the biggest limitation is it does not

reflect the way code is really developed.

Advantages:

 It is the simplest software process model.

 Easy to understand

 Phases are completed one at a time

 Works well for smaller projects

Disadvantages:

 Real projects rarely follow the sequential flow that the model

proposes. Although the linear model can accommodate

iteration, it does so indirectly. As a result, 

changes can cause

confusion as the project team proceeds.

 It is often difficult for the customer to state all requirements

explicitly. The waterfall model requires this and has difficulty

accommodating the natural uncertainty that exists at the

beginning of many projects.

 The customer must have patience. A working version of the

program(s) will not be available until late in the project time

span. A major blunder, if undetected until the working program

is reviewed, can be disastrous.

The Incremental Model:

Situation in which incremental model is applicable:

•

The 

incremental 

model combines 

elements of linear and

parallel process flows.

•

There are many situations in which initial software

requirements are reasonably well defined, but the overall

scope of the development effort prevents a purely linear

process.

•

When an incremental model is used, the first increment is

often a 

core product.

•

That is, basic requirements are addressed but many

supplementary features (some known, others unknown)

remain undelivered.

•

Few of the steps are defined

•

It is iterative in nature.

•

New model for development

•

It provides on the rigid nature(fixed) of sequential approach

•

This method is of great help when organization is low on staffing.

•

This model could be time consuming.

Advantages:

 Useful when staffing is unavailable

 Less costly to change the scope of the project

 Customer can respond to each build.

Disadvantages:

 Cost is higher than waterfall model.

 Needs good planning and design

The RAD Model:

•

Rapid Application Development (RAD) is a modern software process model

that emphasizes a short development cycle. 

•

“high-speed” adaptation (Rapid Application Development )

•

If requirements are well understood and project scope is considered, the

RAD process enables a development team to create a “Fully Functional

System” within a very short period of time (e.g. 60 to 90 days). 

•

This model should be used if domain experts are available with relevant

business knowledge. 

•

Advantages: 

1.

Changing requirements can be accommodated and progress can

be measured.

2. 

Powerful RAD tools 

can reduce development time.

3. Productivity with small team in short development time and quick

reviews, risk control 

increases reusability of components, better

quality.

4. Due to risks in new approach only modularized systems are

recommended through RAD.

5. Suitable for scalable component based systems.

Disadvantages: 

1.

Success of RAD model depends on strong technical team

expertise and skills.

2. Highly skilled developers needed with modeling skills.

3. User involvement throughout life cycle. If developers

&customers are not committed to the rapid fire activities necessary

to complete the System in a much-abbreviated time frame, RAD

projects will fail.

4. May not be appropriate for very large scale systems where the

technical risks are high.

drawback of RAD model.

1. RAD needs enough human resources to create the required

number of RAD teams.

2. If developers and customers are not committed to the rapid

model, the RAD project fails.

3. Rapid-fire activities need to be completed in very short or

small time frame. Time is the major constraint in RAD.

4. RAD has to be modularized in a proper way otherwise creates

a lots of confusions and problems.

5. In case of high performance requirement, RAD cannot be ideal

model.

The Prototype Model:

Situation in which prototyping model

is applicable:

•

Often, a customer defines a set of general objectives for

software, but 

does not identify detailed requirements for

functions and features

.

•

Prototyping iteration is 

planned quickly

, and modeling (in the

form of a “quick design”) occurs.

•

The prototyping paradigm assists you and other stakeholders

to 

better understand what is to be built 

when requirements

are indefinite.

•

The prototyping paradigm begins with communication. You

meet with other stakeholders to define the overall objectives

for the software, identify whatever requirements are known,

and outline areas where further definition is mandatory.

Advantages:

 

Users are actively involved 

in the development.

 Users get 

better understanding of the system 

being

developed.

 

Errors can be detected much earlier

.

 

Quick user feedback 

is available.

Disadvantages:

 Overall 

software quality or maintainability may not get

considered

 when the prototype is being developed.

 An 

inefficient algorithm 

may be implemented.

 

Inappropriate OS or programming language 

maybe used

simply because it is available.

The Spiral Model

•

Using the spiral model, software is developed in a

series of evolutionary releases. During 

early

iterations, the release might be a model 

or

prototype.

•

During 

later iterations, increasingly more complete

versions 

of the engineered system are produced.

•

A spiral model is 

divided into a set of framework

activities 

defined by the software engineering team.

•

Risk

 is considered as each revolution is made.

•

Each pass through the planning region results in

adjustments to the project plan

.

•

Cost and schedule are adjusted 

based on feedback

derived from the customer after delivery.

Advantages:

 The spiral model is a 

realistic approach 

to the

development of large-scale systems and software.

 High amount of risk analysis hence, 

avoidance of

risk 

is enhanced.

Disadvantages:

 It may be difficult to convince customers

(particularly in contract situations) that the

evolutionary approach is controllable.

 It demands considerable risk assessment

expertise and relies on this expertise for success.

 If a 

major risk is not uncovered and managed

,

problems will undoubtedly occur.

Agile Software Development

Agile :

  “Our highest priority is to satisfy the customer through early

and continuous delivery of valuable software“

•

It is an recent approach for Project Management 

•

Cycle-time reduction is most important

•

Model focuses on modularity, iterative, time bound, parsimony,

adaptive, incremental convergent, collaborative approach 

•

Agile process model uses the concept of Extreme Programming

Features of the Agile Software Development Approach

•

Modularity

allows a 

process to be broken into

process to be broken into

components called activities

components called activities

.

•

Iterative

Agile software processes 

focus on short

focus on short

cycles

cycles

. Within each cycle, a certain set of activities

is completed.

•

Time-Bound

set 

time limits 

time limits 

(between one and six

weeks is normal) on each iteration and schedule

•

Parsimony

require a minimal number of 

activities

activities

necessary to reduce risks and achieve their goals

necessary to reduce risks and achieve their goals

.

•

Adaptive

The agile process adapts the process to

attack these 

new found risks

new found risks

.

•

Incremental

partitions the nontrivial system into

increments which may be 

developed in parallel, at

developed in parallel, at

different times, and at different rates

different times, and at different rates

.

•

Convergent

actively 

attacking all of the risks 

attacking all of the risks 

worth

attacking.

•

People-Oriented

Developers that are 

empowered

empowered

raise their productivity, quality, and performance

raise their productivity, quality, and performance

.

•

Collaborative

When a project is developed in

pieces, 

understanding how the pieces fit together 

understanding how the pieces fit together 

is

vital to creating the finished product.

Agile process

Agile Methodologies

•

eXtreme Programming (XP)

eXtreme Programming (XP)

•

Scrum

Scrum

•

Crystal family of methodologies

Crystal family of methodologies

•

Feature-Driven Development (FDD)

•

Adaptive Software Development (ASD)

Adaptive Software Development (ASD)

•

Dynamic System Development Model (DSDM)

Dynamic System Development Model (DSDM)

•

Agile Unified Process (AUP)

eXtreme Programming (XP)

eXtreme Programming (XP)

XP's Four Values

1.

Communication

.  

Most projects fail because of poor

communication.  So implement practices that force

communication in a positive way.

2.

Simplicity.  

Develop the 

simplest product 

that meets the

customer’s needs

3.

Feedback. 

Developers must obtain and value feedback from

the customer, from the system, and from each other.

1.

The same as standard Agile values:  

value customer collaboration

over contract negotiation.

4.

Courage.  

Be prepared to make hard decisions that support

the other principles and practices.

5.

Respect .

The agile team inculcates 

respect 

among it

members, between other stakeholders and team members,

and indirectly, for the software itself.

The XP Process

•

Extreme Programming uses an object-oriented

approach as its preferred development

paradigm and encompasses a set of rules and

practices that occur within the context of four

framework activities:

•

Planning

•

Design

•

Coding

•

Testing

Industrial XP

•

Joshua Kerievsky [Ker05] describes 

Industrial Extreme

Programming 

(IXP) in the following manner:

 “IXP is an 

organic evolution of XP

organic evolution of XP

. It is imbued with XP’s

minimalist, customer-centric, test-driven spirit.

IXP differs most from the original XP in its greater inclusion of

management, its expanded role for customers, and its 

upgraded

technical practices

.”

IXP incorporates six new practices that are designed to help ensure

that an XP project works successfully for significant projects within a

large organization.

Readiness assessment.

Prior to the initiation of an IXP project, the organization should

conduct a 

readiness assessment.

The assessment ascertains whether

(1)

an appropriate development 

environment exists to support IXP

,

(2)

the team will be populated by the 

proper set of stakeholders

,

(3)

the organization has a distinct quality program and supports

continuous improvement

,

(4)

the organizational culture will 

support the new values of an agile

team

,

(5)

 the broader 

project community will be populated 

appropriately.

Project community.

•

When XP is to be applied for a significant project in a

large organization, the concept of the “

team” should

morph into that of a 

community

.

•

A community may have a technologist and

customers

 who are central to the success of a

project as well as many other 

stakeholders

 (e.g.,

legal staff, quality auditors, manufacturing or sales

types) who “are often at the periphery of an IXP

project yet they may play 

important roles on the

project

”

Project chartering.

•

The IXP team assesses the project itself to

determine 

whether an appropriate business

justification for the project exists 

and whether

the project will 

further the overall goals and

objectives of the organization

.

•

Chartering also examines the 

context of the

project to determine how it complements,

extends, or replaces existing systems or

processes

.

Test-driven management.

•

An IXP project requires measurable criteria for

assessing the state of the project and the

progress that has been made to date.

•

Test-driven management 

establishes a series

of measurable “destinations” 

and then defines

mechanisms for determining whether or not

these destinations have been reached.

Retrospectives.

•

An IXP team conducts a 

specialized technical

review

 after a software increment is delivered.

Called a 

retrospective, 

the review examines

“issues, events, and lessons-learned” 

across a

software increment and/or the entire

software release. The intent is to improve the

IXP process.

Continuous learning.

•

Because learning is a vital part of continuous

process improvement, members of the XP team

are encouraged (and possibly, incented) to 

learn

new methods and techniques 

that can lead to a

higher quality product.

Adaptive Software Development (ASD)

Adaptive Software Development (ASD)

•

Speculation

Speculation

uses 

project initiation information

—the

customer’s mission statement, project constraints

(e.g. delivery dates or user descriptions), and basic

requirements—to define the set of release cycles

(software increments) that will be required for the

project.

•

Collaboration 

Collaboration 

It encompasses communication and

teamwork, but it also emphasizes individualism, because

individual creativity plays an important role in collaborative

thinking.

•

People working together must trust one another to

(1)

criticize without hatred,

(2)

Assist without anger,

(3)

work as hard as or harder than they do,

(4)

have the skill set to contribute to the work,

(5)

discuss problems or concerns in a way that leads to effective

action.

•

Learning

Learning

ASD teams learn in three ways:

•

 focus groups ,

•

technical reviews,

•

project postmortems.

•

Software developers often overestimate their own

understanding (of the technology, the process, and the

project) and that learning will help them to improve

their level of real understanding.

Scrum

•

Scrum itself is a framework for 

effective team collaboration

on complex software projects.

•

The team is 

hard working and goal oriented 

even though it

is a small team work. 

•

Scrum is a 

repetitive and incremental framework 

for

project management majorly used in very active software

development.

•

The scrum methodology 

requires openness and trust in the

team

, which these five values of Scrum support 

i.

Openness

ii.

Commitment

iii.

Courage

iv.

Respect

v.

Focus

Advantages:

•

Transparency

 in project development status.

•

Flexibility

 towards the changes.

•

Improved communication, minimum overhead 

in

development process.

•

Productivity 

can be improved.

Disadvantages:

•

Some decisions are 

hard to track in fixed time

span

.

•

There are

 problems to deal with non-functional

requirements 

of the system.

Dynamic Systems Development

Method(DSDM)

DSDM is a,

•

Straight forward framework based on best

principles to start implementing a project structure.

•

Simple

•

Extendible

•

But not calming to be the solution to all kind of

projects.

Crystal

•

Primary goal of this method is to 

deliver useful and

working software

.

•

Crystal is actually comprised of a family of agile

methodologies such as Crystal Clear, Crystal Yellow,

Crystal Orange and others, whose unique

characteristics are driven by several factors such as

team size, system criticality, and project priorities.

•

This Crystal family addresses the realization that each

project may require a slightly tailored 

set of policies,

practices, and processes in order to meet the project 's

unique characteristics

.

selection criteria for software process model