Lecture 3 & 4 | SDLC, Development Methodologies and Models

Fundamentals of Software Engineering
SDLC, Development Methodologies and Models
Lecture 03 & 04
Osamah A. I. Abduljalil
Osamah.Abduljalil@gmail.com
Taiz University
Faculty of Engineering & IT
Software Engineering Dept.

Fundamentals of SE - Osamah Abduljalil 2

Fundamentals of SE - Osamah Abduljalil
Software Process | Development Methodologies
3
◎ A software development methodologies also known as
○ Software development life cycle
○ Software process
◎ When you work to build a product or system, it’s important to go through a series
of predictable steps a road map that helps you create a timely, high-quality result.
◎ A software Process is a framework of the activities, actions and tasks that are
required to build high quality software.

Software Processes Cont.
4
◎ A process: a series of steps involving activities, constrains, and
resources that produce an output
◎ A process involves a set of tools and techniques
◎ Many different software processes but all involve:
○ Specification –what the system should do;
○ Design and implementation –the organization of the system and
implementing the system;
○ Validation – checking that it does what the customer wants;
○ Evolution – changing the system in response to changing
customer needs.

Software Development Methodologies cont.
5
Software development methodologies are a key concept of SE
To overcome s/w crisis
SE
To develop a s/w product
The development team must identify suitable methodology for particular project.

Software Development Life Cycle (SDLC)
6
◎ SDLC stands for Software Development Life Cycle. SDLC is a
process that consists of a series of planned activities to
develop or alter the Software Products.
◎ SDLC process is used by the software industry to design,
develop and test high quality software.
◎ It aims to produce the quality software that meets or exceeds
customer expectations, reaches completion within time and
budget.
◎ A “life-cycle” or a software process is the organizational
framework for a project.

SDLC Phases
7
1. Planning and Requirements Analysis
2. Defining Requirements
3. Designing the Software
4. Building or Developing the Software
5. Testing the Software
6. Deployment and Maintenance

SDLC Phases Cont.
8
◎ 1. Planning & Requirement Analysis
◎ Requirement analysis is the most important and fundamental stage in
SDLC.
◎ It is performed by the senior members of the team with inputs from all the
stakeholders and domain experts or SMEs in the industry.
◎ Planning for the quality assurance requirements and identification of the
risks associated with the project is also done at this stage.

SDLC Phases Cont.
9
◎ 2. Defining Requirements
◎ Once the requirement analysis is done the next step is to clearly define
and document the software requirements and get them approved from the
project stakeholders.
◎ This is done through ‘SRS’ — Software Requirement Specification
document which consists of all the product requirements to be designed
and developed during the project life cycle.

SDLC Phases Cont.
10
◎ Feasibility Study
◎ Economic: Can we complete the project within the budget or not?
◎ Legal: Can we handle this project as cyber law and other regulatory
framework/compliances.
◎ Operation feasibility: Can we create operations which is expected by the
client?
◎ Technical: Need to check whether the current computer system can
support the software.
◎ Schedule: Decide that the project can be completed with in the given
schedule or not.

SDLC Phases Cont.
11
◎ 3. Designing the Software
◎ Based on the requirements specified in SRS, usually more than one design
approach for the product architecture is proposed.
◎ Modules
◎ UML Diagram
◎ ERD

SDLC Phases Cont.
12
◎ 4. Developing the Software
◎ In this stage of SDLC the actual development starts and the product is
built.
◎ The programming code is generated as per DDS during this stage.
◎ Developers have to follow the coding guidelines defined by their
organization and programming tools like compilers, interpreters,
debuggers etc. are used to generate and implement the code.

SDLC Phases Cont.
13
◎ 5. Testing the Software
◎ This stage is usually a subset of all the stages as in the modern SDLC
models, the testing activities are mostly involved in all the stages of SDLC.
◎ However this stage refers to the testing only that stage of the software
where defects are reported, tracked, fixed and retested, until the software
reaches the quality standards defined in the SRS.

SDLC Phases Cont.
14
◎ 5. Deployment and Maintenance
◎ Once the software is tested and no bugs or errors are reported then it is
deployed.
◎ Then based on the feedback, the software may be released as it is or with
suggested enhancements in the target segment.
◎ After the software is deployed then its maintenance starts.
◎ Maintenance
○ Bug fixing - bugs are reported because of some scenarios which are
not tested at all
○ Upgrade - Upgrading the application to the newer versions of the
Software
○ Enhancement - Adding some new features into the existing software

SDLC Models
15
◎ To help understand and implement the
SDLC phases various SDLC models have
been created by software development
experts, universities, and standards
organizations.

Reasons for Using SDLC Models
16
◎ Provides the base for project planning, estimating & scheduling.
◎ Provides framework for standard set of terminologies, activities &
deliverables.
◎ Provides mechanism for project tracking & control.
◎ Increases visibility of project progress to all stakeholders.

Advantages of Choosing an appropriate SDLC Models
17
◎ Increased development speed
◎ Increased product quality
◎ Improved tracking & control
◎ Improved client relations
◎ Decreased project risk
◎ Decreased project management overhead

Classic Waterfall Model
18
◎ Oldest and most well-known SDLC model.
◎ Follows a sequential step-by-step process from requirements analysis to
maintenance.
◎ The waterfall Model shows the software development process in a linear
sequential flow. This means that any phase in the development process
begins only if the previous phase is complete. - no turning back.
◎ Invented in 1970. The waterfall model, sometimes called the classic life
cycle
◎ Systems that have well-defined and understood requirements are a good
fit for the Waterfall Model.

Classic Waterfall Model cont.
19

20
◎ Advantages:
◎ Easy to understand, easy to use
◎ Provides structure to inexperienced staff
◎ Milestones are well understood
◎ Sets requirements stability
◎ Good for management control (plan, staff, track)
◎ Process and results are well documented.
◎ Works well when quality is more important than cost or schedule

21
◎ Disadvantages:
◎ No feedback
◎ No parallelism
◎ High Risk
◎ Poor model for long and ongoing projects.
◎ 60% efforts in Maintenance

22
◎ When to use :
◎ Requirements are very well known
◎ Product definition is stable
◎ Technology is understood
◎ There are no ambiguous requirements
◎ New version of an existing product

Iterative Waterfall Model
23
◎ Iterative waterfall allows you to return to the previous phase and adjust
requirements and, if necessary, some modifications.
◎ In the iterative waterfall model, the next phase can only begin when the
previous phase is completed as the waterfall model.

Iterative Waterfall Model cont.
24

Incremental Model
25
◎ Module by Module development
◎ In incremental model the whole requirement is divided into various
builds. Multiple development cycles take place here, making the life cycle
a “multi-waterfall” cycle.
◎ Cycles are divided up into smaller, more easily managed modules.
◎ Each subsequent release of the system adds function to the previous
release, until all designed functionality has been implemented.
◎ Maximum customer intraction

Incremental Model Cont.
26

27
◎ Advantages:
◎ Generates working software quickly and early during the software life
cycle.
◎ This model is more flexible – less costly to change scope and
requirements.
◎ It is easier to test and debug during a smaller iteration.
◎ In this model customer can respond to each built.
◎ Lowers initial delivery cost.
◎ Easier to manage risk because risky pieces are identified and handled
during it’d iteration.

28
◎ Disadvantages:
◎ Needs good planning and design.
◎ Needs a clear and complete definition of the whole system before it can be
broken down and built incrementally.
◎ Total cost is higher than waterfall.

29
◎ When to use the Incremental model:
◎ 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.

Prototype Model
30
◎ The Software Prototyping refers to building software application prototypes which
displays the functionality of the product under development, but may not actually
hold the exact logic of the original software.
◎ Customer is not clear with idea.
◎ Throwing away model
◎ Developers build a prototype during the requirements phase
◎ Prototype is evaluated by end users
◎ Users give corrective feedback
◎ Developers further refine the prototype
◎ When the user is satisfied, the prototype code is brought up to the standards needed
for a final product.
◎ Good for technical and requirement risks

Prototype Model cont.
31
◎ Advantages:
◎ Customers can “see” the system requirements as they are being gathered
◎ Developers learn from customers
◎ A more accurate end product
◎ Allows for flexible design and development
◎ Unexpected requirements accommodated

Prototype Model cont.
32
◎ Disadvantages:
◎ Time-consuming
◎ Increase in cost of development
◎ Customer can confuse between the actual product and prototype.
◎ Change in the requirement usually expand the scope of the product
beyond its original plan and thus increase the complexity.

Reuse–based Model
33
◎ Software reuse is the use of existing software or software knowledge
to build new software for an individual or an organization.
◎ Software reuse is also called as “Code Reuse”.
◎ Systematic software reuse is still the most promising strategy for
increasing productivity and improving quality in the software
industry.
◎ Example of software reuse is software library.

Reuse–based Model cont.
34
◎ Advantages:
○ It can reduce total cost of software development.
○ The risk factor is very low.
○ It can save lots of time and effort.
○ It is very efficient in nature.

Reuse–based Model cont.
35
◎ Disadvantages:
○ It doesn't always work as intended in real-world situations.
○ Lack of tool support and knowledge.
○ Sometimes using old system component, that is not compatible with
new version of component, this may lead to an impact on system
evolution.
○ Compromises in requirements may lead to a system that does not
fulfill requirement of user.

Lecture 3 & 4 | SDLC, Development Methodologies and Models

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