What is System and its elements? What SDLC, Waterfall Model, Prototype model, Spiral Model and RAD Model

1. (BAST -306)
Software Analysis
and Design
Dr Sharmila Sharad More,
Assistant Professor , Dept Of Science and Computer
Science,
MIT, ACSC,Alandi, Pune

3. Unit-I Introduction to SDLC –
(9)
Content we have to discuss in
Unit –I-
 What is System and its elements?
 What SDLC,
 Waterfall Model,
 Prototype model,
 Spiral Model and
 RAD Model
Systems development is systematic process
which includes phases such as planning,
analysis, design, deployment, and
maintenance
Whenever we starts developing a new product, it is
important to follow the system development life cycle.

4. System:
 A system is a organized combination of resources working together to convert inputs into
useful output.
 It is derived from a Greek word ‘system’.
 A system is an organized grouping of interdependent components working together
according a plan to fulfill predetermined objectives ( or linked together according to a plan to
achieve a specific goal.)
Characteristics of system:
· Predetermined Objectives
· It can be further subdivided
· All components can be interdependent or interrelated
E.g.- Traffic Management System, Payroll System, Automatic Library System,Information System.
Types of System:
1. · Physical System
2. · Abstract System
3. · Open System
4. · Close System
5. · Deterministic System
6. · Probabilistic System
7. · Introduction System
What is System and its elements?

5. 1. Physical System:
A physical system can be tangible or visible which can be touch and also be counted.
Physical system can be operated statically or dynamically.
2. Abstract System:
It can be conceptual or intangible.
For ex: A model of organization represents the concept.
3. Open System:
An open system is that interacts freely with outside environment and also it can be affected
from outside environment. When the environment changes the open system must also
change in order to adopt itself to the environment otherwise it will be fail.
4. Deterministic System:
Deterministic system operates in a manner that stat of the system at a time is already
determined and we can also predict the next state of the system without error.
For ex: The output of computer system is deterministic.
5. Probabilistic System:
The probabilistic system works in a predictable manner. If we can predict the stat of the
system then it is probabilistic.
For ex: Economic forecasting

6. Elements of system:
A system’s objectives are expressed in terms of output is needs to produce, the inputs are the
data which are processed while the output i.e. information are the outcome of the process.
In addition there are two more components
i. Control
It makes the system to operate within supportable performance levels. Control of the system
is the decision maker that controls the activities of accepting input, process & producing the
output.
ii. Feedback
It is the information on how well a system is performing & it is essential for system
modifications.
System may use feedback for control the information generated by comparing results with
acceptable level of performance (standards) and informing the control elements of the
difference is termed as feedback.
In feedback control the output is fed back to input. It allows to be majored against some
standards and making adjustment in the processing accordingly.

7. The software development life cycle (SDLC)
 The software development life cycle (SDLC) is a process which is used to develop software.
 SDLC is a step by step procedure need to be followed by the organization to design and develop a high quality
product.
 The phases of software development life cycle are which describes that how to develop, maintain particular software.
 The life cycle aims to develop a good quality product/software.
 SDLC produces intermediate products that can be reviewed to check whether they work according to customer
requirement.
 It should result in a high quality system that meets customer expectations, reaches completion within time and cost
evaluations, and works effectively and efficiently in the current and planned Information Technology infrastructure.
It is a well defined process by which a system is planned, developed and implemented.
The system development starts with the requirement for improving their business system.
Whenever we starts developing a new product, it is important to follow the system development life
cycle.

8. There are 8 activities involves in SDLC :-
 · Preliminary Investigation (Problem
Identification)
 · Feasibility study
 · System analysis
 · System designing
 · Development of software(Coding)
 · System testing
 · Implementation & Evaluation
 · Maintenance

9. Detailed Description of SDLC

10. 1. Preliminary Investigation OR Problem Identification:
One of most difficult task of the system analyst is identifying the real problem of the existing system.
It defines the user requirements or what the user expects from the new system. This also includes the
rough idea of the resource requirements as well as estimated time for completion and number of
persons expected to be involve in each phase.
Problem identification helps in :- i. Defining a problem
ii. Setting proper system goal
iii. Determining the boundaries of the project by
considering the limitations of available resources
2. Feasibility study:
It determine the possibility of either improving the existing system or developing the complete new
system. It helps to obtain an overview of the problem and to get rough assessment of whether physical
solution exist. The purpose of feasibility study is to determine whether the requested system
successfully realizable.
There are four aspects of feasibility study :- i. Technical feasibility
ii. Economical feasibility
iii. Operational feasibility
iv. Behavioural feasibility

11. i. Technical feasibility:
It involves the required and existing computer system, hardware, software & to what extent it can support
the proposed application.
It answers following questions :-
o Whether the system can be carried out with existing equipment’s ?
o Whether the existing software is enough ?
o If a new technology is required how best it can be implemented ?
ii. Economic feasibility:
It involves post benefit analysis to determine the benefit and savings that are expected from new system
and compared with costs. It benefits out weight cost then decision is made to design and implement new
system.
iii. Operational feasibility:
It concerns with human, organisational and political aspects. It covers technical performance as well as
acceptance within the organisation. It determines the general attitude and job skills of existing personals
and whether any restructuring of jobs will be acceptable to the current user.
iv. Behavioural feasibility:
It includes how strong the reaction of staff will be towards the development of new system that involves
computer’s use in their daily work. So resistant to change is identified.

12. 3. System analysis:
It involves detailed understanding of all important facts of the business area under investigation. This require data
collection from a verity of sources such as questionnaires, forms, interviews, study of existing documents. It can be
involved the direct observation in the organisation and collected documents to understand the whole existing system.
4. System designing:
In this process the primary object is to identify user requirements and to build a system that satisfies these requirements.
Design of the system is mainly the logical design that can be sketch on a paper or on a computer. It includes physical
design elements, describes the data to be inputted.
The process involved in manipulation of data & output design represents:-
i. File structure, storage devices etc
ii. Database is also designed in this phase
iii. Changes to be made in the organisational structure of the firm are outlines
iv. Input, Output, files, forms and procedures are planned
v. Finally standards for testing, documentation, system control are designed.
5. Development of software: The actual software development process begins at this phase.
Development is a phase where detailed design is used to actually construct and build the system. In this phase the system
is decided whether to buy commercial software or to develop new customized program with the help of the programmers.
The choice depends upon the cost of software and cost of programming.
6. System testing:
Testing is a process of making sure that the program performs the intended task. Once the system is designed it should be
tested for validity. During this phase the system is used experimentally to ensure that software does not fail and it will
work according to its specification. It is tested with special test data.

13. 7. Implementation & Evaluation:
This is the final phase of development. It consists of installing hardware, programs, collecting data and
organizing people to interact with and run the system. In this phase user actually starts using the system
therefore it also involves training of users and provides friendly documentation.
Evaluation is the process of verifying the capability of a system after it put into operation to see whether
it meets the objective or not. It includes response time, overall reliability and limitations user behaviour.
8. Maintenance:
It is process of incorporating changes in the implemented existing system.
i. Enhancement: Adding new functions or additional capability of the system.
ii. Adaptation: Customizing the software to run in a new environment.
iii. Correction : Correcting the bugs in the existing software

14. • The Waterfall Model was the first Process Model to be introduced.
• It is also referred to as a linear-sequential life cycle model.
• It is very simple to understand and use.
• In a waterfall model, each phase must be completed before the
next phase can begin and there is no overlapping in the phases.
• Waterfall approach was first SDLC Model to be used
widely in Software Engineering to ensure success of the
project.
• In "The Waterfall" approach, the whole process of
software development is divided into separate
phases.
• In this Waterfall model, typically, the outcome of one phase
acts as the input for the next phase sequentially. ….called as
Cascading Model
Waterfall Model

15. When to use -Waterfall Model :-
 Waterfall model can be used when -Requirements are not changing
frequently
 Application is not complicated and big
 Project is short
 Requirement is clear
 Environment is stable
 Technology and tools used are not dynamic and is stable
 Resources are available and trained

16. Requirement Gathering stage  During this phase, detailed requirements of the software system
to be developed are gathered from client
Design Stage  Plan the programming language, for Example Java, PHP, .net
or database like Oracle, MySQL, etc.
 Or other high-level technical details of the project
Coding Stage  After design stage, it is built stage, that is nothing but coding the
software
Test Stage  In this phase, you test the software to verify that it is built as per
the specifications given by the client.
Deployment stage  Deploy the application in the respective environment
Maintenance stage  Once your system is ready to use, you may later require change
the code as per customer request

17. Advantages Dis-Advantages
 Before the next phase of development, each phase
must be completed
 Error can be fixed only during the phase
 Suited for smaller projects where requirements are
well defined
 It is not desirable for complex project where
requirement changes frequently
 They should perform quality assurance test
(Verification and Validation) before completing each
stage
• Testing period comes quite late in the developmental
process
 Elaborate documentation is done at every phase of the
software's development cycle
 Documentation occupies a lot of time of developers
and testers
 Project is completely dependent on project team with
minimum client intervention
• Clients valuable feedback cannot be included with
ongoing development phase
 Any changes in software is made during the process
of the development
 Small changes or errors that arise in the completed
software may cause a lot of problems
Advantages and Disadvantages of Waterfall-Model

18. Prototype Model
• In this Prototype Model before designing phase, a
prototype is developed, tested, reviewed and approved by
the customer, after that design will be ready for coding,
testing, installation and maintenance will takes place.
• This prototype is prepared based on the customer
requirements.
• Prototype testing is checking for the required
components are present or not.
• This Prototype Model is same as waterfall model, but
in this model we need to develop prototype and
customer interaction will be there. Since there is
customer interaction there will be less chance of
rejection.

19. When to use Prototype model:
• Whenever the customer not clears about the requirement in this situation we generally go for
prototype model.
• If it is complex project then prototype model makes clear understand the requirement.
• Prototyping make sure that the customer constantly work with the system and provide a feedback
about the system.
• By using this prototype, customer can understand the requirements of desired system and also
the customer can get an “actual feel” of the system.
• It is an attractive idea for complex and bigger systems.

20. Advantages Disadvantages
Customer satisfaction exists, because customer can feel the
product at very early stage.
There are no parallel deliverables
If there is missing functionality can be identified easily It is a time consuming if customer ask for
changes in prototype
There will be less chance of software rejection This methodology may increase the system
complexity as scope of the system may
expand beyond original plans.
Requirement changes are allowed. The invested effort in the preparation of
prototypes may be too much if not properly
monitored.
Due to customer approval we can find the errors at early
stage
Customer may get confused in the
prototypes and real systems.
Customer involvement will be there in the development
where its leads to better solutions for any confusion /
complexity / difficult functions
The developed prototype can be re-used by developer and
test engineer.

21. Spiral Model
• The spiral model combines the idea of iterative development with the systematic, controlled
aspects of the waterfall model.
• This Spiral model is a combination of iterative development process model and sequential linear
development model i.e. the waterfall model with a very high emphasis on risk analysis.
• It allows incremental releases of the product or incremental refinement through each iteration
around the spiral.
The spiral model has four phases.
A software project repeatedly passes through these phases in iterations called Spirals.
 Identification
 Design
 Construct or Build
 Evaluation and Risk Analysis

23.  Identification
• This phase starts with gathering the business requirements in the baseline spiral.
• In the subsequent spirals as the product matures, identification of system requirements, subsystem
requirements and unit requirements are all done in this phase.
• This phase also includes understanding the system requirements by continuous communication
between the customer and the system analyst.
• At the end of the spiral, the product is deployed in the identified market.
 Design
• The Design phase starts with the conceptual design in the baseline spiral and involves architectural
design, logical design of modules, physical product design and the final design in the subsequent
spirals.

24.  Construct or Build
• The Construct phase refers to production of the actual software product at every spiral.
• In the baseline spiral, when the product is just thought of and the design is being developed a
POC (Proof of Concept) is developed in this phase to get customer feedback.
• Then in the subsequent spirals with higher clarity on requirements and design details a working
model of the software called build is produced with a version number.
• These builds are sent to the customer for feedback.
 Evaluation and Risk Analysis
• Risk Analysis includes identifying, estimating and monitoring the technical feasibility and
management risks, such as schedule slippage and cost overrun.
• After testing the build, at the end of first iteration, the customer evaluates the software and
provides feedback.

25. Advantages Disadvantages
Changing requirements can be accommodated. Management is more complex.
Allows extensive use of prototypes End of the project may not be known early.
Requirements can be captured more
accurately.
Not suitable for small or low risk projects and could be
expensive for small projects.
Users see the system early. Process is complex
Development can be divided into smaller parts
and the risky parts can be developed earlier
which helps in better risk management
Spiral may go on indefinitely.
Large number of intermediate stages requires excessive
documentation.

26. • RAD model is Rapid Application
Development model.
• It is a type of incremental model.
• 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.
RAD model
• This can quickly give the customer something
to see and use and to provide feedback
regarding the delivery and their requirements.

27. The phases in the rapid application development (RAD) model are:
 Business modeling: The information flow is identified between various business functions.
 Data modeling: Information gathered from business modeling is used to define data objects that
are needed for the business.
 Process modeling: Data objects defined in data modeling are converted to achieve the business
information flow to achieve some specific business objective. Description are identified and
created for CRUD of data objects.
 Application generation: Automated tools are used to convert process models into code and the
actual system.
 Testing and turnover: Test new components and all the interfaces.

28. When to use RAD model:
• RAD should be used when there is a need to create a system that can be modularized in 2-3
months of time.
• It should be used if there’s high availability of designers for modeling and the budget is high
enough to afford their cost along with the cost of automated code generating tools.
• RAD SDLC model should be chosen only if resources with high business knowledge are
available and there is a need to produce the system in a short span of time (2-3 months).

29. Advantages Disadvantages
Reduced development time. Depends on strong team and individual
performances for identifying business
requirements.
Increases reusability of components. Only system that can be modularized can be
built using RAD.
Quick initial reviews occur. Requires highly skilled developers/designers.
Integration from very beginning solves a lot
of integration issues.
High dependency on modeling skills
Encourages customer feedback. Inapplicable to cheaper projects as cost of
modeling and automated code generation is
very high.