Software Engineering Perspective and Specialized Process Models

Software Engineering
KCS-601, Unit-I, 1.3
Dr APJ Abdul Kalam Technical
University, Lucknow
By
Dr Anuranjan Misra
1
Dr Anuranjan Misra
innovation
Ambassador
Ministry of Education,
Government of India
& Professor & Dean,
GNIOT, Greater Noida

Perspective and Specialized
Process Models

A GENERIC PROCESS MODEL
⚫ A process was defined as a collection of work activities, actions, and tasks
that are performed when some work product is to be created. Each of these
activities, actions, and tasks reside within a framework or model that defines
their relationship with the process and with one another.
⚫ The software process is represented schematically in Figure 2.1. Referring
⚫ The software process is represented schematically in Figure 2.1. Referring
to the figure, each framework activity is populated by a set of software
engineering actions.
⚫ Each software engineering action is defined by a task set that identifies the
work tasks that are to be completed, the work products that will be
produced, the quality assurance points that will be required, and the
milestones that will be used to indicate progress.

⚫ A generic process framework for software engineering defines
five framework activities—communication, planning,
modeling, construction, and deployment. In addition, a set of
umbrella activities—project tracking and control, risk
management, quality assurance, configuration management,
technical reviews, and others—are applied throughout the
process.
⚫ A linear process flow executes each of the five framework
⚫ A linear process flow executes each of the five framework
activities in sequence, beginning with communication and
culminating with deployment (Figure 2.2a).
⚫ An iterative process flow repeats one or more of the
activities before proceeding to the next (Figure 2.2b).
⚫ An evolutionary process flow executes the activities in a
“circular” manner.
(Figure 2.2c).
⚫ A parallel process flow (Figure 2.2d) executes one or more
activities in parallel with otheractivities.

Typical umbrella activities include:
Software project tracking and control—allows the software team to assess
progress against the project plan and take any necessary action to maintain
the schedule.
Risk management—assesses risks that may affect the outcome of the project
or the quality of the product.
Software quality assurance—defines and conducts the activities required to
ensure software quality
Technical reviews—assesses software engineering work products in an effort
to uncover and remove errors before they are propagated to the next activity.
to uncover and remove errors before they are propagated to the next activity.
Measurement—defines and collects process, project, and product measures
that assist the team in delivering software that meets stakeholders‘ needs;
can be used in conjunction with all other framework and umbrella activities.
Software configuration management—manages the effects of change
throughout the software process.
Reusability management—defines criteria for work product reuse and
establishes mechanisms to achieve reusable components.
Work product preparation and production—encompasses the activities
required to create work products such as models, documents, logs, forms,
and lists.

PRESCRIPTIVE PROCESS MODELS
⚫The Waterfall Model
⚫Spiral Model
⚫V Shaped Model
⚫V Shaped Model
⚫RAD Model
⚫Iterative Model
⚫Prototype Model

The Waterfall Model
⚫ Thewaterfall model, sometimescalled theclassic lifecycle, suggestsa
systematic, sequential approach to software development that begins with
customer specification of requirements and progresses through planning,
modeling, construction, and deployment. Linear-sequential model or
classic life cycle model.
classic life cycle model.

Features of waterfall model:
• It is very simple to understand and use.
• In a waterfall model, each phase must be completed
fully before the next phase can begin.
• This type of model is basically used for the for the
project which is small and there are no uncertain
requirements.
• At the end of each phase, a review takes place to
determine if the project is on the right path and
whether or not to continue or discard the project.
• Testing phase starts only after the development is
complete.
• In waterfall model phases do not overlap.
• Documentation is produced in each and every step

Advantages of waterfall model-
⚫ This model works forsmall projects because the requirementsare
understood verywell.
⚫ Thewaterfall model is simple and easy tounderstand, implement,
and use.
⚫ All the requirementsare known at the beginning of the project,
hence it iseasy to manage.
⚫ Documentation helps for future reference
⚫ Documentation helps for future reference
Disadvantages of thewaterfall model
⚫ The problemswith this model are uncovered, until the software
testing.
⚫ Requirement analysis is done initially, sometime its nit possible
to state all requirements initially.
⚫ Theamountof risk is high.
⚫ This model is notgood forcomplexand objectoriented projects.
⚫ Customer can see the model only at the end

When to use the waterfall model:
• This model is used only when the requirements
are very well known, clear and fixed.
• Product definition is stable.
• Technology is understood.
• Technology is understood.
• There are no ambiguous requirements
• The project is short.

The Spiral model
⚫Spiral model is a risk driven process model.
⚫Spiral model is iterative in nature
⚫In spiral model, an alternate solution is provided if the risk is
found in the risk analysis, then alternate solutions are suggested
and implemented.
and implemented.
⚫It is a combination of prototype and sequential model or
waterfall model.
⚫In one iteration all activities are done, for large project's the
output is small.
⚫The framework activities of the spiral model are as shown in
the following figure.

• The spiral model is similar to the incremental model, with
more emphasis placed on risk analysis.
• The spiral model has four phases: Planning, Risk Analysis,
Engineering and Evaluation.
• A software project repeatedly passes through these phases in
• A software project repeatedly passes through these phases in
iterations (called Spirals in this model).
• The baseline spiral, starting in the planning phase,
requirements is gathered and risk is assessed.
• Each subsequent spiral builds on the baseline spiral.

Planning Phase:
Requirements are gathered during the planning phase.
Requirements like ‛BRS‘ that is ‛Business Requirement
Specifications’ and SRS‘ that is System Requirement
specifications’.
Risk Analysis:
In the risk analysis phase, a process is undertaken to identify
risk and alternate solutions.
A prototype is produced at the end of the risk analysis phase.
A prototype is produced at the end of the risk analysis phase.
If any risk is found during the risk analysis then alternate
solutions are suggested and implemented.
Engineering Phase:
In this phase software is developed, along with testing at the
end of the phase.
Hence in this phase the development and testing is done.
Evaluation phase:
This phase allows the customer to evaluate the output of the
project to date before the project continues to the next spiral.

Advantages of Spiral Model
⚫ It reduces high amount of risk.
⚫ It is good for large and critical projects.
⚫ It gives strong approval and documentation control.
⚫ Requirement changes can be made easily at every stage.
⚫ Additional Functionality can be added at a later date.
⚫ In spiral model, the software is produced early in the life cycle process.
⚫ In spiral model, the software is produced early in the life cycle process.
Disadvantages of Spiral Model
⚫ It can be costly to develop a software model.
⚫ It is not used for small projects.
⚫ Risk analysis requires highly specific expertise.
⚫ Project‘s success is highly dependent on the risk analysis phase

When to use Spiral model:
• When costs and risk evaluation is important
• When project is not expected within a specific limited time span
• For medium to high-risk projects
• Users are unsure of their needs
• Requirements are complex.
• Significant changes are expected (research and exploration)

V- Shaped Model means Verification and Validation model. A
variation in the representation of the waterfall model is called the V-
Shaped Model.
Just like the waterfall model, the V-Shaped life cycle is a sequential
V-Shaped Model
path of execution of processes.
Each phase must be completed before the next phase begins.
Testing of the product is planned in parallel with a corresponding
phase of development

⚫ As a software team moves down the left side of the V, basic problem
requirements are refined into progressively more detailed and technical
representations of the problem and its solution.
⚫ Once code has been generated, the team moves up the right side of the V,
essentially performing a series of tests (quality assurance actions) that
validate each of the models created as the team moved down the left side.

Phases of V-Model
Requirements
• Requirements like BRS and SRS begin the life cycle model just
like the waterfall model.
• But, in this model before development is started, a system test
plan is created.
• The test plan focuses on meeting the functionality specified in
the requirements gathering.
The high-level design (HLD)
• This phase focuses on system architecture and design.
• It provides overview of solution, platform, system, product and
service/process.
• An integration test plan is created in this phase as well in order
to test the pieces of the software systems ability to work
together.

Phases of V-Model
The low-level design (LLD)
• This phase is where the actual software components are designed.
• It defines the actual logic for each and every component of the
system.
• Class diagram with all the methods and relation between classes
comes under LLD.
• Component tests are created in this phase as well.
Implementation
Implementation
• In this phase , all coding takes place.
• Once coding is complete, the path of execution continues up the
right side of the V where the test plans developed earlier are now
put to use.
Coding
• This is at the bottom of the V-Shape model.
• Module design is converted into code by developers.

Advantages of V-model
• Simple and easy to use.
• Testing activities like planning, test designing happens well before
coding. This saves a lot of time. Hence higher chance of success
over the waterfall model.
• Proactive defect tracking – that is defects are found at early stage.
• Avoids the downward flow of the defects.
• Works well for small projects where requirements are easily
• Works well for small projects where requirements are easily
understood.
Disadvantages of V-model
• Very rigid and least flexible.
• Software is developed during the implementation phase, so no
early prototypes of the software are produced.
• If any changes happen in midway, then the test documents along
with requirement documents has to be updated

When to use the V-model
• The V-shaped model should be used for small to medium
sized projects where requirements are clearly defined and
fixed.
• The V-Shaped model should be chosen when ample
• The V-Shaped model should be chosen when ample
technical resources are available with needed technical
expertise.
• High confidence of customer is required for choosing the V-
Shaped model approach. Since, no prototypes are produced,
there is a very high risk involved in meeting customer
expectations.

RAD Model/(RAPID APPLICATION DEVELOPMENT MODEL)
• RAD model is a type of incremental process model in which
there is extremely short development cycle.
• It is a type of incremental model.
• In RAD model the components or functions are developed in
• In RAD model the components or functions are developed in
parallel as if they were mini projects.
• The developments are time boxed, delivered and then
assembled into a working prototype.
• This can quickly give the customer something to see and use
and to provide feedback regarding the delivery and their
requirements.

Features of RAD model
• Using a RAD Model, a software product can be developed
within 60 to 90 days of time.
• Various phases of RAD model are
• Requirement gathering,
• Planning,
• Planning,
• Analysis,
• Design and
• Deployment
When to use RAD model
• When there is a need to create a system 2-3 months of
time.
• Only when the resources with high business knowledge
are available

Advantages of the RAD model:
• Reduced development time.
• Increases reusability of components
• Quick initial reviews occur
• Encourages customer feedback
• Integration from very beginning solves a lot of integration
issues.
Disadvantages of RAD Model:
Disadvantages of RAD Model:
• Requires highly skilled developers/designers.
• Requires multiple teams and large number of people to
work on a project.
• Need Heavy resources
• If there is no proper modularization, then RAD project
would fail.
• Adopting new technologies is difficult.

Iterative Process Models
• The iterative development model develops a system
by building small portions of all the features. This
helps to meet the initial scope quickly and release it
for feedback.
• In the iterative model, you start off by implementing
• In the iterative model, you start off by implementing
a small set of software requirements. These are
then enhanced iteratively in the evolving versions
until the system is completed. This process model
starts with part of the software, which is then
implemented and reviewed to identify further
requirements.

In this Iterative model, the whole requirement is divided into
various builds. During each iteration, the development module
goes through the requirements, design, implementation and
testing phases. Each subsequent release of the module adds
function to the previous release. The process continues till the
complete system is ready as per the requirement.

This model is most often used in the following scenarios −
• Requirements of the complete system are clearly defined and
understood.
• Major requirements must be defined; however, some
functionalities or requested enhancements may evolve with time.
• There is a time to the market constraint.
• There is a time to the market constraint.
• A new technology is being used and is being learnt by the
development team while working on the project.
• Resources with needed skill sets are not available and are planned
to be used on contract basis for specific iterations.
• There are some high-risk features and goals which may change in
the future.

Advantages of Iterative model
• The advantages of the and Incremental SDLC Model are as
follows −
• Some working functionality can be developed quickly and
early in the life cycle.
• Results are obtained early and periodically.
• Parallel development can be planned.
• Parallel development can be planned.
• Progress can be measured.
• Less costly to change the scope/requirements.
• Testing and debugging during smaller iteration is easy.
• Risks are identified and resolved during iteration; and each
iteration is an easily managed milestone.
• Easier to manage risk - High risk part is done first.
• With every increment, operational product is delivered.

Advantages of Iterative model
• Issues, challenges and risks identified from each increment
can be utilized/applied to the next increment.
• Risk analysis is better.
• It supports changing requirements.
• Initial Operating time is less.
• Initial Operating time is less.
• Better suited for large and mission-critical projects.
• During the life cycle, software is produced early which
facilitates customer evaluation and feedback.

The Prototyping model
• Prototype is defined as first or preliminary form using
which other forms are copied or derived.
• Prototype model is a set of general objectives for
software.
• It does not identify the requirements like detailed
input, output.
input, output.
• It is software working model of limited functionality.
• In this model, working programs are quickly
produced.
• It is difficult to do modifications in earlier development
phases of linear model. In such cases Iterative approach is
adopted.
• The evolutionary process model is iterative model

Features of Prototyping model
• The basic idea here is that instead of freezing the
requirements before a design or coding can proceed, a
throwaway prototype is built to understand the requirements.
• This prototype is developed based on the currently known
requirements.
• By using this prototype, the client can get an actual feel of the
system, since the interactions with prototype can enable the
system, since the interactions with prototype can enable the
client to better understand the requirements of the desired
system.
• Prototyping is an attractive idea for complicated and large
systems for which there is no manual process or existing
system to help determining the requirements.
• The prototype is usually not complete systems and many of
the details are not built in the prototype. The goal is to
provide a system with overall functionality.

The different phases of Prototyping model are:
1.Communication
In this phase, developer and customer meet and discuss
the overall objectives of the software.
2.Quick design
Quick design is implemented when requirements are
known. It includes only the important aspects like input
known. It includes only the important aspects like input
and output format of the software. It focuses on those
aspects which are visible to the user rather than the detailed
plan. It helps to construct a prototype.
3.Modeling quick design
This phase gives the clear idea about the development of
software because the software is now built. It allows the
developer to better understand the exact requirements.

The different phases of Prototyping model are:
4.Construction of prototype
The prototype is evaluated by the customer itself.
5.Deployment, delivery, feedback
5.Deployment, delivery, feedback
If the user is not satisfied with current prototype then it refines
according to the requirements of the user.The process of
refining the prototype is repeated until all the requirements of
users are met. When the users are satisfied with the
developed prototype then the system is developed on the basis
of final prototype.

Advantages of Prototyping Model
⚫ Prototype model need not know the detailed input, output, processes,
adaptability of operating system and full machine interaction.
⚫ In the development process of this model users are actively involved.
⚫ The development process is the best platform to understand the system by
the user.
⚫ Errors are detected much earlier.
⚫ Gives quick user feedback for better solutions.
⚫ It identifies the missing functionality easily. It also identifies the confusing
⚫ It identifies the missing functionality easily. It also identifies the confusing
or difficult functions.
Disadvantages of Prototyping Model:
⚫ The client involvement is more and it is not always considered by the
developer.
⚫ It is a slow process because it takes more time for development.
⚫ Many changes can disturb the rhythm of the development team.
⚫ It is a thrown away prototype when the users are confused with it.

When to use Prototype model:
Prototype model should be used when the desired system needs to
have a lot of interaction with the end users.
• Typically, online systems, web interfaces have a very high
amount of interaction with end users, are best suited for
Prototype model.
• It might take a while for a system to be built that allows ease of
use and needs minimal training for the end user.
• Prototyping ensures that the end users constantly work with the
system and provide a feedback which is incorporated in the
prototype to result in a useable system.
• They are excellent for designing good human computer interface
systems.

Disadvantages of Iterative model
• More resources may be required.
• Although cost of change is lesser, but it is not very suitable for changing
requirements.
• More management attention is required.
• System architecture or design issues may arise because not all
• System architecture or design issues may arise because not all
requirements are gathered in the beginning of the entire life cycle.
• Defining increments may require definition of the complete system.
• Not suitable for smaller projects.
• Management complexity is more.
• End of project may not be known which is a risk.
• Highly skilled resources are required for risk analysis.
• Projects progress is highly dependent upon the risk analysis phase.

Software Engineering Perspective and Specialized Process Models

Software Engineering Perspective and Specialized Process Models

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