Software Requirements Engineering - SRE also called as Requirements Engineering

20CSP43 - Software
Engineering
Requirements
UNIT – 1
Software Engineering Concepts
Ms. Preetha V AP/CSE

UNIT - I
 Software Engineering Concepts
 Introduction- Nature of Software - The changing nature of Software – Software
Myths – Characteristics of Software -The Software Process: The Process
Framework - Umbrella Activities.

Software Engineering
 Software Engineering is an engineering branch related to the evolution of
software product using well-defined scientific principles, techniques, and
procedures.
 Software Engineering provides a standard procedure to design and develop a
software.


The software is a collection of integrated programs.
 Software subsists of carefully-organized instructions and code written by
developers on any of various particular computer languages.
 Computer programs and related documentation such as requirements, design
models and user manuals.
 Engineering is the application of scientific and practical knowledge
to invent, design, build, maintain, and improve frameworks, processes,
etc.

Why is Software Engineering required?
 Software Engineering is required due to the following reasons:
 To manage Large software
 For more Scalability
 Cost Management
 To manage the dynamic nature of software
 For better quality Management

Characteristics of a good software engineer
 The features that good software engineers should possess are as follows:
 Exposure to systematic methods, i.e., familiarity with software engineering
principles.
 Good technical knowledge of the project range (Domain knowledge).
 Good programming abilities.
 Good communication skills. These skills comprise of oral, written, and
interpersonal skills.
 High motivation.

What is the nature of software in software
engineering?
 Software is:
 (1) instructions (computer programs) that when executed provide desired
features, function, and performance;
 (2) data structures that enable the programs to adequately manipulate
information, and
 (3) document that describes the operation and use of the programs.

Changing Nature of Software
 System Software:
System software is a collection of programs which are written to service other
programs. Some system software processes complex but determinate,
information structures. Other system application process largely
indeterminate data. Sometimes when, the system software area is
characterized by the heavy interaction with computer hardware that requires
scheduling, resource sharing, and sophisticated process management.
 Examples of system software include operating systems (OS) (like macOS,
Linux, Android, and Microsoft Windows), computational science software,
game engines, search engines, industrial automation, and software as a
service applications.

 Application Software:
Application software is defined as programs that solve a specific business
need. Application in this area process business or technical data in a way that
facilitates business operation or management technical decision making. In
addition to convention data processing application, application software is
used to control business function in real time.
 A collection of Microsoft software including MS Office, PowerPoint, Word,
Excel, and Outlook.
 Common Internet browsers like Google Chrome, Safari, Firefox, etc.
 Graphics and designing software such as Canva, Adobe Photoshop, CorelDraw,
and AutoCAD.

 Engineering and Scientific Software:
This software is used to facilitate the engineering function and task. however
modern application within the engineering and scientific area are moving
away from the conventional numerical algorithms. Computer-aided design,
system simulation, and other interactive applications have begun to take a
real-time and even system software characteristic.
 Software is written for specific applications Examples are software
like MATLAB, AUTOCAD, PSPICE, ORCAD, etc.

 Embedded Software:
Embedded software resides within the system or product and is used to
implement and control feature and function for the end-user and for the
system itself. Embedded software can perform the limited and esoteric
function or provided significant function and control capability.
 Image processing systems found in medical imaging equipment. Fly-by-wire
control systems found in aircraft. Motion detection systems in security
cameras. Traffic control systems found in traffic lights.

 Product-line Software:
Designed to provide a specific capability for use by many
different customers, product line software can focus on the
limited and esoteric marketplace or address the mass consumer
market.
 Software product lines often have many features in common
and operate using the same core programming. This may
include a line of products like devices, in which your phone,
smartwatch and laptop all function together and use versions of
the same software.

 Web Application:
It is a client-server computer program which the client runs on the web
browser. In their simplest form, Web apps can be little more than a set of
linked hypertext files that present information using text and limited
graphics. However, as e-commerce and B2B application grow in importance.
Web apps are evolving into a sophisticate computing environment that not
only provides a standalone feature, computing function, and content to the
end user.
 Google Docs. Google Workspace, the Google Office suite, is one of the most
popular collections of web apps. ...
 Netflix. One of the top video-streaming platforms is also a web app. ...
 Trello. ...
 Basecamp. ...
 Microsoft Office. ...
 Uber. ...
 eBay. ...

 Artificial Intelligence Software:
Artificial intelligence software makes use of a nonnumerical algorithm to
solve a complex problem that is not amenable to computation or
straightforward analysis. Application within this area includes robotics, expert
system, pattern recognition, artificial neural network, theorem proving and
game playing.
 Virtual assistants like Siri and Alexa.
 Recommendation systems used in e-commerce platforms.
 Fraud detection in financial institutions.
 Autonomous vehicles.
 NLP for chatbots and customer service.

Software Myths:
 Most, experienced experts have seen myths or superstitions (false beliefs or
interpretations) or misleading attitudes (naked users) which creates major
problems for management and technical people. The types of software-related
myths are listed below.

(i) Management Myths:
Managers are often under pressure for software development
under a tight budget, improved quality, and a packed
schedule, often believing in some software myths. Following
are some management myths.
 Myth1:
 We have all the standards and procedures available for software
development.
 Fact:
 Software experts do not know all the requirements for the software
development.
 And all existing processes are incomplete as new software development is
based on new and different problem.

 Myth 2
 Falling behind on schedule could be taken care of by adding more
programmers.
Reality 2
 Adding more human resources to already late projects worsens the problem.
Developers working on the project have to educate the newcomers, further
delaying the project. Also, newcomers are far less productive than developers
already working on them. As a result, time spent on educating newcomers
could not meet the immediate reduction in work.

 Myth 3
 If a project is outsourced to a third party, we could just relax and wait for
them to build it.
Reality 3
 If an organisation is not able to manage and control software projects
internally, then the organisation will suffer invariably when they outsourced
the project.

Customer Myths
 Customer Myths are generally due to false expectations by customers, and
these myths end up leaving customers with dissatisfaction with the software
developers. Following are some customer myths.

 Myth 1:
 A general statement of intent is enough to start writing plans (software
development) and details of objectives can be done over time.
 Fact:
 Official and detailed description of the database function, ethical
performance, communication, structural issues and the verification process
are important.
 Unambiguous requirements (usually derived iteratively) are developed only
through effective and continuous
communication between customer and developer.

 Myth 2:
 Software requirements continually change, but change can be easily
accommodated because software is flexible
 Fact:
 It is true that software requirements change, but the impact of change varies
with the time at which it is introduced. When requirements changes are
requested early (before design or code has been started), the cost impact is
relatively small. However, as time passes, the cost impact grows rapidly—
resources have been committed, a design framework has been established,
and change can cause upheaval that requires additional resources and major
design modification.

Practitioner’s Myths
Developers often work under management pressure to
complete software within a timeframe, with fewer resources
often believing in these software myths. Following are some
practitioners’ myths.
 Myth 1
 Once the software is developed or the code is delivered to the customer, the
developer's work ends.
Reality 1
 A significant chunk of developers' work, i.e., 50-60 % of all the efforts
expended on software, will be spent after the customer provides the
software. Major requirements would get found missing, and new bugs may get
discovered, and so on.

 Myth 2
 Software testing could only be possible when the software program starts
running.
Reality 2
 Quality of software could be measured at any phase of development by
applying some QA mechanism.

 Myth 3
 Unnecessary Documentation slows down the process of software
development.
Reality 3
 Software engineering is about creating a quality product at every level and
not about adding unnecessary work. Proper documentation of software helps
us guide the user and enhance the quality, which reduces the amount of
rework.

Characteristics of Software
 Software Characteristics are classified into six major components.
ISO( International Organization for Standardization)/IEC (International
Electrotechnical Commission) 9126 is an international standard proposed to
make sure ‘quality of all software-intensive products’ which includes a
system like safety-critical where in case of failure of software lives will be in
danger.

Functionality
 Functionality refers to the set of features and capabilities that a software
program or system provides to its users.
 Examples of functionality in software include:
 Data storage and retrieval
 Data processing and manipulation
 User interface and navigation
 Communication and networking
 Security and access control
 Reporting and visualization
 Automation and scripting

The more functionality a software has, the more powerful and versatile it is, but
also the more complex it can be.

Reliability
 Reliability is a characteristic of software that refers to its ability to perform
its intended functions correctly and consistently over time. Reliability is an
important aspect of software quality, as it helps ensure that the software will
work correctly and not fail unexpectedly.
 Examples of factors that can affect the reliability of software include:
 Bugs and errors in the code
 Lack of testing and validation
 Poorly designed algorithms and data structures
 Inadequate error handling and recovery
 Incompatibilities with other software or hardware

 To improve the reliability of software, various techniques, and methodologies
can be used, such as testing and validation, formal verification, and fault
tolerance.

Efficiency
 It refers to the ability of the software to use system resources in the most
effective and efficient manner.
 Efficiency is a characteristic of software that refers to its ability to use
resources such as memory, processing power, and network bandwidth in an
optimal way.
 High efficiency means that a software program can perform its intended
functions quickly and with minimal use of resources, while low efficiency
means that a software program may be slow or consume excessive resources.

 Examples of factors that can affect the efficiency of the software include:
 Poorly designed algorithms and data structures
 Inefficient use of memory and processing power
 High network latency or bandwidth usage
 Unnecessary processing or computation
 Unoptimized code

To improve the efficiency of software, various techniques, and methodologies can
be used, such as performance analysis, optimization, and profiling.

Usability
 It refers to the extent to which the software can be used with ease. the
amount of effort or time required to learn how to use the software.
Required functions are:

Maintainability
 It refers to the ease with which modifications can be made in a software
system to extend its functionality, improve its performance, or correct
errors.

Portability
 A set of attributes that bears on the ability of software to be transferred from
one environment to another, without minimum changes.

Various Characteristics of Software in
Software Engineering
 Software is developed or engineered; it is not manufactured in the
classical sense:
 Although some similarities exist between software development and hardware
manufacturing, few activities are fundamentally different.
 In both activities, high quality is achieved through good design, but the
manufacturing phase for hardware can introduce quality problems than software.

 The software doesn’t “wear out.”:
 Hardware components suffer from the growing effects of many other
environmental factors. Stated simply, the hardware begins to wear out.
 Software is not susceptible to the environmental maladies that cause hardware to
wear out.
 When a hardware component wears out, it is replaced by a spare part.
 There are no software spare parts.
 Every software failure indicates an error in design or in the process through which
the design was translated into machine-executable code. Therefore, the software
maintenance tasks that accommodate requests for change involve considerably
more complexity than hardware maintenance. However, the implication is clear—
the software doesn’t wear out. But it does deteriorate.

 The software continues to be custom-built:
 A software part should be planned and carried out with the goal that it tends to be
reused in various projects.
 Current reusable segments encapsulate the two pieces of information and the
preparation that is applied to the information, empowering the programmer to
make new applications from reusable parts.
 In the hardware world, component reuse is a natural part of the engineering
process.

Software Processes
 The term software specifies to the set of computer programs, procedures and associated
documents (Flowcharts, manuals, etc.) that describe the program and how they are to be
used.

A software process is the set of activities and associated outcome that produce a software
product. Software engineers mostly carry out these activities. These are four key process
activities, which are common to all software processes. These activities are:

Software specifications: The functionality of the software and constraints on its operation
must be defined.
Software development: The software to meet the requirement must be produced.
Software validation: The software must be validated to ensure that it does what the
customer wants.
Software evolution: The software must evolve to meet changing client needs.

Software Process Framework
 Software Process Framework is an abstraction of the software development
process. It details the steps and chronological order of a process. Since it
serves as a foundation for them, it is utilized in most applications. Task sets,
umbrella activities, and process framework activities all define the
characteristics of the software development process.

 Software process includes:
 Tasks – focus on a small, specific objective.
 Action – set of tasks that produce a major work product.
 Activities – group of related tasks and actions for a major objective.

Umbrella activities
 Umbrella activities are a series of steps or procedures followed by a software
development team to maintain the progress, quality, changes, and risks of
complete development tasks. These steps of umbrella activities will evolve
through the phases of the generic view of software development.

Umbrella activities
 Typical umbrella activities are:
 1. Software project tracking and controlIn this activity, the developing team accesses project
plan and compares it with the predefined schedule.
If these project plans do not match with the predefined schedule, then the required actions are
taken to maintain the schedule.
 2. Risk managementRisk is an event that may or may not occur.
If the event occurs, then it causes some unwanted outcome. Hence, proper risk management is
required.
 3. Software Quality Assurance (SQA)SQA is the planned and systematic pattern of activities
which are required to give a guarantee of software quality.
For example, during the software development meetings are conducted at every stage of
development to find out the defects and suggest improvements to produce good quality
software.

Umbrella activities
 4. Formal Technical Reviews (FTR)FTR is a meeting conducted by the technical
staff.
 The motive of the meeting is to detect quality problems and suggest
improvements.
 The technical person focuses on the quality of the software from the customer
point of view.
 5. MeasurementMeasurement consists of the effort required to measure the
software.
 The software cannot be measured directly. It is measured by direct and indirect
measures.
 Direct measures like cost, lines of code, size of software etc.
 Indirect measures such as quality of software which is measured by some other
factor. Hence, it is an indirect measure of software.

Umbrella activities
 6. Software Configuration Management (SCM)It manages the effect of
change throughout the software process.
 7. Reusability managementIt defines the criteria for reuse the product.
The quality of software is good when the components of the software are
developed for certain application and are useful for developing other
applications.
 8. Work product preparation and productionIt consists of the activities that
are needed to create the documents, forms, lists, logs and user manuals for
developing a software.

Software Requirements Engineering - SRE also called as Requirements Engineering

Software Requirements Engineering - SRE also called as Requirements Engineering

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