Agile Dev. II

© People Strategists www.peoplestrategists.com Slide 1 of 42
Agile Development
and Design Patterns - I

Objectives
In this session, you will learn to:
Identify SDLC
Identify agile model
Identify design patterns

Identify SDLC
What is SDLC?

Identifying SDLC (Contd.)
SDLC is the acronym of Software Development Life Cycle.
It is also called as software development process.
It is a term used in information systems and software engineering to
describe a process for planning, creating, testing, and deploying an
information system.
It is a framework defining tasks performed at each step in the
software development process.
The SDLC aims to produce a high quality software that meets or
exceeds customer expectations, reaches completion within times
and cost estimates.
SDLC defines a methodology for improving the quality of software
and the overall development process.

The following figure depicts graphical representation of the various
stages of SDLC.
SDLC
Planning
Defining
Designing
Building
Testing
Deployment

A typical SDLC consists of the following stages:
1. Planning and Requirement Analysis:
 It is the most important and fundamental stage in SDLC, which is performed by
the senior members of the team.
 Planning for the quality assurance requirements and identification of the risks
associated with the project is also done in the planning stage.
2. Defining:
 After the requirement analysis is finalized, the next step is to define and
document the product requirements in Software Requirement Specification
(SRS) document.
3. Designing:
 Based on the requirements specified in SRS, usually more than one design
approach for the product architecture is proposed and documented in a
DDS - Design Document Specification.
4. Building:
 At this stage of SDLC the actual development of product starts and finish. The
programming code is generated as per DDS during this stage.

5. Testing:
 At this stage, product's defects are reported, tracked, fixed, and retested, until
the product reaches the quality standards defined in the SRS.
6. Deployment:
 Once the product is tested and ready to be deployed it is released formally in
the appropriate market.
 After that, based on the feedback, the product may be released as it is or with
suggested enhancements in the targeting market segment

Identifying Different SDLC Models
The most important and popular SDLC models followed in the
industry are:
Waterfall Model:
 The waterfall model was first process model to be introduced.
 It is also referred to as a linear-sequential life cycle model.
 In a waterfall model, each phase must be completed before the next
phase can begin and there is no overlapping in the phases.
Iterative Model:
 It starts with a simple implementation of a subset of the software
requirements and iteratively enhances the evolving versions until the full
system is implemented.
 In this model, at each iteration, design modifications are made and new
functional capabilities are added.
V-Model:
 It is an extension of the waterfall model and is based on association of a
testing phase for each corresponding development stage.
 This is a highly disciplined model and next phase starts only after
completion of the previous phase.

Identifying Different SDLC Models (Contd.)
RAD Model:
 Rapid application development (RAD) is a software development
approach that uses least planning in favor of rapid prototyping.
 A prototype is a working model that is functionally equivalent to a
component of the product.
 In this model the functional modules are developed in parallel as
prototypes and are integrated to make the complete product for faster
product delivery.
Big Bang Model:
 This model comprises of focusing all the possible resources in software
development and coding, with very little or no planning.
 This model is ideal for small projects with one or two developers working
together

Identifying Agile Development
Agile is an approach that promotes continuous iteration of
development and testing throughout the software development life
cycle of the project.
It is an alternative to traditional project management, typically used in
software development.
It is a combination of iterative and incremental process models with
focus on process adaptability and customer satisfaction.
In agile the tasks are divided to small time frames to deliver specific
features for a release.
Agile methods break the product into small incremental builds. These
builds are provided in iterations.
Each build is incremental in terms of features; the final build holds all
the features required by the customer.

Identifying Agile Development (Contd.)
The following figure graphically illustrate the agile model.

Principles of Agile Development
The agile development is based on the following principles:
1. Our highest priority is to satisfy the customer through early and
continuous delivery of valuable software.
2. Welcome changing requirements, even late in development. Agile
processes harness change for the customer's competitive advantage.
3. Deliver working software frequently, from a couple of weeks to a couple
of months, with a preference to the shorter timescale.
4. Business people and developers must work together daily throughout the
project.
5. Build projects around motivated individuals. Give them the environment
and support they need, and trust them to get the job done.
6. The most efficient and effective method of conveying information to and
within a development team is face-to-face conversation.
7. Working software is the primary measure of progress.

Principles of Agile Development (Contd.)
8. Agile processes promote sustainable development. The sponsors,
developers, and users should be able to maintain a constant pace
indefinitely.
9. Continuous attention to technical excellence and good design enhances
agility.
10. Simplicity – the art of maximizing the amount of work not done – is
essential.
11. The best architectures, requirements, and designs emerge from
self–organizing teams.
12. At regular intervals, the team reflects on how to become more effective,
then tunes and adjusts its behavior accordingly.

Agile vs Waterfall Method
The following figure depicts the differences between the agile and
waterfall models.
Agile Waterfall
Agile method proposes incremental
and iterative approach to software
design.
Documentation attends less priority
than software development.
The agile process is broken into
individual models that designers work
on.
The customer has early and frequent
opportunities to look at the product
and make decision and changes to
the project.
Agile model is considered
unstructured compared to the
waterfall model.
Development of the software flows
sequentially from start point to end
point.
Documentation is a top priority and
can even use for training staff and
upgrade the software with another
team.
The design process is not broken into
an individual models.
The customer can only see the
product at the end of the project.
Waterfall model are more secure
because they are so plan oriented.

Agile vs Waterfall Method (Contd.)
The following figure depicts the successful rate of the agile model over
the waterfall model.

Advantages of Agile Development
Agile development has the following advantages:
Customer satisfaction by rapid, continuous delivery of useful software.
People and interactions are emphasized rather than process and tools.
Customers, developers and testers constantly interact with each other.
Working software is delivered frequently (weeks rather than months).
Face-to-face conversation is the best form of communication.
Close, daily cooperation between business people and developers.
Continuous attention to technical excellence and good design.
Regular adaptation to changing circumstances.
Even late changes in requirements are welcomed.

Limitations of the Agile Development
Agile development has the following limitations.
In case of some software deliverables, especially the large ones, it is
difficult to assess the effort required at the beginning of the software
development life cycle.
There is lack of emphasis on necessary designing and documentation.
The project can easily get taken off track if the customer representative
is not clear what final outcome that they want.
Only senior programmers are capable of taking the kind of decisions
required during the development process. Therefore, it has no place for
newbie programmers, unless combined with experienced resources.

Exploring the Agile Model
When to use
Agile model?

Exploring the Agile Model (Contd.)

Exploring Agile Methodologies
The following figure depicts the various methodologies of the agile
model.

Scrum is one of the most important method used in agile development
because of its very simplicity and flexibility.
Scrum believes in empowering the development team and believes in
working in small teams.
It comprises of three roles and their responsibilities, which are
displayed in the following figure.
Scrum
Scrum meetingScrum master
Product
owner
Prepare product
backlogs
Team organize
tasks

Scrum master:
 Is responsible for setting up the team, sprint meeting and removes hurdles to
progress.
Product owner:
 Creates product backlog, prioritizes the backlog and is responsible for the
delivery of the functionality at each iteration.
Scrum team:
 Manages its own work and organizes the work to complete the sprint or cycle.
Product Backlog:
Is a repository where requirements are tracked with details on the No. of
requirements to be completed for each release.
It is maintained and prioritized by scrum master and distribute it to the
scrum team.
Scrum (Contd.)

eXtreme Programming (XP):
This technique is mostly used when demands or requirements of the
customers constantly changed.
It advocates frequent "releases" of the product in short development
cycles, which integrally improves the productivity of the system and also
introduces a checkpoint where any customer requirements can be easily
implemented.
The XP develops software keeping customer in the target.
eXtreme Programming (XP)

Dynamic Software Development Method (DSDM)
DSDM:
Is a Rapid Application Development (RAD) methodology used in software
development and provides an agile project delivery framework.
the important aspect of DSDM is that the users are required to be involved
actively, and the teams are given the power to make decisions.
Products whose delivery change frequently use this technique.
The techniques used in DSDM are:
 Time boxing
 MoSCoW rules
 Prototyping

Introducing Design Pattern
How to resolve the
problems that
commonly occurs in
software design?

Introducing Design Pattern (Contd.)
Design pattern:
Is a language-independent tactics used to solve common object-oriented
design problems.
Is used to speed up the development process by providing tested, verified
development paradigms.
Provides general solutions, which are documented in a format that doesn't
require specifics tied to a particular problem.
Allows developers to communicate using well-known, well understood
names for software interactions.
Resides in the domain of modules and interconnections.
Is not a finished design that transformed directly into code. In fact, it is a
description or template that is used resolve problems, which can be used in
many different situations.

What is Gang of Four (GOF)?
Authors of the book named Design Patterns, are often referred to as the
GOF, or Gang of Four.
The Design Patterns book was published by four authors Erich Gamma,
Richard Helm, Ralph Johnson and John Vlissides, in 1994.
The Design Patterns book describes various development techniques
and pitfalls
According to GOF design patterns are primarily based on the following
principles of object orientated design.
Program to an interface not an implementation
Favor object composition over inheritance

Usage of Design Pattern
In software development, two main usages of design patterns are:
Common platform for developers
 Design patterns provide a standard terminology and are specific to
particular scenario.
 For example, a singleton design pattern signifies use of single object so
all developers familiar with single design pattern will make use of single
object and they can tell each other that program is following a singleton
pattern.
Best Practices
 Design patterns have been evolved over a long period of time and they
provide best solutions to certain problems faced during software
development.
 Learning these patterns helps unexperienced developers to learn
software design in an easy and faster way.

Exploring Design Patterns
Design patterns are further classified into following categories:
Creational patterns
Structural patterns
Behavioral patterns
J2EE patterns

Creational Patterns
Creational Patterns:
Provide a way to create objects while hiding the creation logic, rather
than instantiating objects directly using new operator.
Are design patterns that deal with object creation mechanisms, trying to
create objects in a manner suitable to the situation.
Provide ways to instantiate single objects or groups of related objects.
Different types of creational patterns are:
Abstract Factory:
 Is used to control class instantiation.
 is used to provide a client with a set of related or dependent objects.
 The "family" of objects created by the factory is determined at run-time
according to the selection of concrete factory class.
 Provides one level of interface higher than the factory pattern. It is used to
return one of several factories.

 In the given figure, abstract factory pattern with two Kinds of products created by
two concrete factories.
 Implementation for the abstract factory pattern is given in the embedded code.
Creational Patterns (Contd.)
Client
AbstractProductA AbstractProductB
AbstractFactory
+createProductA():AbstractProductA
+createProductB():AbstractProductB
ProductA1 ProductA2 ProductB2ProductB1
ConcreateFactory2
ConcreteFactory1

Singleton:
 Ensures that only one object of a particular class is ever created. All further
references to objects of the singleton class refer to the same underlying
instance.
 Are extensible by the subclass by defining subclass final.
 Make a method or a variable public or/and static.
 Is useful when a single, global point of access to a limited resource is required.
 The following figure depicts the implementation of the singleton pattern:
 Implementation for the Prototype is given in the embedded code.
Singleton
-Singleton():
+getInstance(): Singleton
-instance: Singleton

Builder:
 Is used to create complex objects from simple objects step by step.
 It uses the Factory Builder pattern to decide which concrete class to initiate in
order to build the desired type of object.
 It is used to isolate code for construction and representation.
 It gives you finer control over the construction process.

 The following figure depicts the implementation of the builder pattern:
Director
+construct(builder: Builder): void
ConcreateBuilder
+buildPart(): void
+getResult():Product
Builder
+buildPart(): void
Product
For all objects in structure:
builder.buildPart()

The participants classes in this pattern are:
 Builder: class specifies an abstract interface for creating parts of a product
object.
 ConcreteBuilder: constructs and puts together parts of the product by
implementing the Builder interface. It defines and keeps track of the
representation it .
 Director: class constructs the complex object using the Builder interface.
 Product: represents the complex object that is being built.
Implementation for the Builder pattern is given in the embedded code.

Prototype:
 Instantiate a new object by copying all of the properties of an existing object,
creating an independent clone.
 Is useful when the construction of a brand new object, using the new
operator, is inefficient.
 Is used when there are many subclasses that differ only in the kind of objects,
 Is used when a system needs independent of how its objects are created,
composed, and represented.
 It helps in dynamic binding or loading a method and add and remove objects
at runtime.
 It use one instance to finish job just by changing its state or parameters.
 Ensures that only one instance of a class is created.
 Provides a global point of access to the object

 The following figure depicts the implementation of the prototype pattern:
Prototype
+Clone(): Object
ConcreatePrototype1
+Clone(): Object
ConcreatePrototype2
+Clone(): Object
Client
+Operation:void
//Only the first object is
created:
ConcretePrototype obj1 =
new ConcretePrototype();
ConcretePrototype obj2 =
new ConcretePrototype();

The classes participating to the prototype pattern are:
 Client: creates a new object by asking a prototype to clone itself.
 Prototype: declares an interface for cloning itself.
 ConcretePrototype: implements the operation for cloning itself.
Implementation for the prototype is given in the embedded code.

Summary
SDLC is the acronym of Software Development Life Cycle.
SDLC is a term used in information systems and software engineering to
describe a process for planning, creating, testing, and deploying an
information system.
SDLC defines a methodology for improving the quality of software and
the overall development process.
A typical SDLC consists of the following stages:
Planning and Requirement Analysis
Defining
Designing
Building
Testing
Deployment

Summary (Contd.)
The most important and popular SDLC models followed in the industry
are:
Waterfall Model
Iterative Model
V-Model
RAD Model
Big Bang Model
Agile Model
Agile is an approach that promotes continuous iteration of development
and testing throughout the software development life cycle of the
project.
In agile the tasks are divided to small time frames to deliver specific
features for a release.

Summary (Contd.)
Agile methods break the product into small incremental builds. These
builds are provided in iterations.
Scrum is one of the most important method used in agile development
because of its very simplicity and flexibility.
eXtreme Programming (XP) technique is mostly used when demands or
requirements of the customers constantly changed.
Is a Rapid Application Development (RAD) methodology used in
software development and provides an agile project delivery
framework.
Design pattern is a language-independent tactics used to solve common
object-oriented design problems.
Design pattern provides general solutions, which are documented in a
format that doesn't require specifics tied to a particular problem.

Summary (Contd.)
Design pattern allows developers to communicate using well-known,
well understood names for software interactions.
Creational patterns provide a way to create objects while hiding the
creation logic, rather than instantiating objects directly using new
operator.
Abstract factory is used to provide a client with a set of related or
dependent objects.
Singleton ensures that only one object of a particular class is ever
created. All further references to objects of the singleton class refer to
the same underlying instance.
Builder pattern is used to create complex objects from simple objects
step by step.
Prototype pattern instantiate a new object by copying all of the
properties of an existing object, creating an independent clone.

Agile Dev. II

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