SDLC Methodologies

Business Analysis
Training
SDLC

Classification: Restricted
Agenda
• SDLC (Software Development Life Cycle)
• Types of SDLC Methodologies
• Waterfall Approach
• Incremental Approach
• Iterative Approach
• Difference between Incremental and Iterative
• Prototype Approach
• Spiral Approach

Software
It should be noted that although software is thought of as a program, it can be
anything that runs on a computer.
Software is a general term for the various kinds of programs used to
operate computers and related devices

Software Development Life Cycle
• The software development life cycle (SDLC) is a framework defining tasks
performed at each step in the software development process.
•SDLC is a structure followed by a
development team within the
software organization.
•It consists of a detailed plan
describing how to develop,
maintain and replace specific
software.
•SDLC consists of the following
activities:

Types of SDLC Methodologies
• Waterfall Model - linear framework type
• Incremental Model - combination of linear and iterative framework type
• Iterative Model- Repetitious framework type
• Agile – “Agile Development” is an umbrella term for several iterative and
incremental software development methodologies

Waterfall Approach
• Waterfall Model:

Waterfall Approach
• The waterfall model is documentation-intensive, with earlier phases
documenting what must be done and subsequent phases adding greater
detail and defining how it should be done.
• The output from one phase serves as the input to the next phase, with the
project flowing from one step to the next in a waterfall fashion.
• An important consideration for the Waterfall model is that fixes or
modifications are often put off until the maintenance phase.
• This can be very costly, as the cost to correct a problem gets higher with
each successive phase.

Waterfall Approach - Advantages
• System is well documented.
• Phases correspond with project management phases.
• Cost and schedule estimates may be lower and more accurate.
• Details can be addressed with more engineering effort if software is large or
complex.

Waterfall Approach - Disadvantages
• All risks must be dealt with in a single software development effort.
• Because the model is sequential, there is only local feedback at the
transition between phases.
• A working product is not available until late in the project.
• Progress and success are not observable until the later stages. If a mistake
or deficiency exists in the documentation of earlier phases, it may not be
discovered until the product is delivered.
• Corrections must often wait for the maintenance phase.
• High amounts of risk and uncertainty.
• Not a good model for complex and object-oriented projects.
• Poor model for long and ongoing projects.
• Not suitable for the projects where requirements are at a moderate to
high risk of changing.

When to use Waterfall Model?
• Requirements are very well known, clear and fixed.
• Product definition is stable.
• Technology is understood.
• There are no ambiguous requirements
• Ample resources with required expertise are available freely
• The project is short.

Incremental Approach

Incremental Approach
• The incremental model is essentially a series of waterfall cycles.
• The requirements are known at the beginning of the project and are
divided into groups for incremental development.
• A core set of functions is identified in the first cycle and is built and
deployed as the first release.
• The software development cycle is repeated, with each release adding
more functionality until all requirements are met.
• Each development cycle acts as the maintenance phase for the previous
software release.
• While new requirements that are discovered during the development of a
given cycle can be implemented in subsequent cycles, this model assumes
that most requirements are known up front.
• A modification to the incremental model allows development cycles to
overlap. That is, a subsequent cycle may begin before the previous cycle is
complete.

Incremental Approach - Advantages
• Generates basic working model quickly.
• More flexible – less costly to change scope.
• Customer can respond in each build thus more responsive to user needs
than the waterfall model.
• A usable product is available with the first release, and each cycle results
in greater functionality.
• The project can be stopped any time after the first cycle and leave a
working product.
• Project management may be easier for smaller, incremental projects.
• Testing may be easier on smaller portions of the system.
• Lowers initial delivery costs.

Incremental Approach - Disadvantages
• The majority of requirements must be known in the beginning.
• Formal reviews may be more difficult to implement on incremental releases
than on a complete system.
• Because development is spread out over multiple iterations, interfaces
between modules must be well-defined in the beginning.
• Cost and schedule overruns may result in an unfinished system.
• Operations are impacted as each new release is deployed.
• Users are required to learn how to use a new system with each
deployment.

When to use Incremental Approach
• This model can be used when the requirements of the complete system
are clearly defined and understood.
• Major requirements must be defined; however, some details can evolve
with time.
• There is a need to get a product to the market early.
• A new technology is being used
• Resources with needed skill set are not available.
• There are some high risk features and goals.

Iterative Approach
• Iterative development is best defined in terms of its processes that allow
for dynamic development rather than any single defined method or
approach.

Iterative Approach
Definition
A process for arriving at a decision or a desired result by repeating rounds of
analysis or a cycle of operations. The objective is to bring the desired decision
or result closer to discovery with each repetition
For example, a project can be divided into 12 one- to four-week iterations.
• The system is tested at the end of each iteration, and the test feedback is
immediately incorporated at the end of each test cycle.
• The time required for successive iterations can be reduced based on the
experience gained from past iterations.
• The system grows by adding new functions during the development
portion of each iteration.

Iterative Approach
• Iteration comes from word Iterative means repetitious.
• Iteration means the act of repeating a process usually with the aim of
approaching a desired goal or target or result. Each repetition of the
process is also called an "iteration," and the results of one iteration are
used as the starting point for the next iteration.

Iterative Approach - Principles
Principles of Iterative Development
• Time has priority over functionality
• Get the most bang for the buck
• Power to the customer
• Empowered teams – Decision speed & competency
• Adaptability
• Short life cycles
• Fast feedback
You can’t stop the
clock!
The customer is always
right

Iterative Approach - Advantages
• More adaptable to changes.
• Allows for early detection of risks associated with a given project
• QA can be performed at the end of each iteration.
• Project managers are in a better position to assess the impact of changes
on the delivery dates.
• Early visible progress.
• A continuous improvement methodology.
• Corrective actions can be taken at the end of each iteration.

Iterative Approach - Disadvantages
• It is difficult to freeze requirements, and they may continue to change in
later iterations because of increasing customer demands. As a result,
more iterations may be added to the project, leading to project delays
and cost overruns.
• The project requires a very efficient change control mechanism to
manage changes made to the system during each iteration.
• More time spent in review and analysis
• A lot of steps that need to be followed in this model
• Delay in one phase can have detrimental effect on the software as a
whole

Difference between Incremental and Iterative
Incremental development is a staging and scheduling strategy in which
various parts of the system are developed at different rates, and integrated
as they are completed.
Iterative development is a rework scheduling strategy in which time is set
aside to revise and improve parts of the system.

Prototype Approach
What is Prototyping?
• Software prototyping, can be defined as incomplete versions of the
software program being developed.
• A prototype typically simulates only a few aspects of the features of the
eventual program, and may be completely different from the eventual
implementation.
Purpose of Prototyping?
• 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 client to better
understand the requirements of the desired system.

Prototyping
Throwaway prototyping:
• Creation of a model that will eventually be discarded rather than becoming
part of the final delivered software.
• After preliminary requirements gathering is accomplished, a simple
working model of the system is constructed to visually show the users
what their requirements may look like when they are implemented into a
finished system.
• The user interface is what the user sees as the system, and by seeing it in
front of them, it is much easier to grasp how the system will work

Type of Prototyping
One method of creating a Throwaway Prototype is Paper Prototyping. The
prototype is implemented using paper and pencil, and thus mimics the
function of the actual product, but does not look at all like it
Another method to easily build high fidelity Throwaway Prototypes is to use a
GUI Builder and create a click dummy, a prototype that looks like the goal
system, but does not provide any functionality

Spiral Approach

Spiral Model Application
• When there is a budget constraint and risk evaluation is important.
• For medium to high-risk projects.
• Long-term project commitment because of potential changes to economic
priorities as the requirements change with time.
• Customer is not sure of their requirements which is usually the case.
• Requirements are complex and need evaluation to get clarity.
• New product line which should be released in phases to get enough
customer feedback.

Spiral Approach Steps
A first prototype of the new system is constructed from the preliminary
design. This is usually a scaled-down system, and represents an approximation
of the characteristics of the final product
A second prototype is evolved by a fourfold procedure:
• evaluating the first prototype in terms of its strengths, weaknesses,
and risks;
• defining the requirements of the second prototype;
• planning and designing the second prototype;
• constructing and testing the second prototype
• The existing prototype is evaluated in the same manner as was the
previous prototype, and, if necessary, another prototype is developed
from it according to the fourfold procedure outlined above
• The final system is constructed, based on the refined prototype
• The final system is thoroughly evaluated and tested.

Thank you

SDLC Methodologies

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