Requirement Engineering

1211501075 – Christian Yonathan Sillueta

Overview
• Describe requirement engineering activities
and processes.
• Look into techniques, problems, challenges of:
– Feasibility Studies
– Requirements elicitation
– Requirement specification
– Requirements Validation
– Requirements management and evolution

Importance of Requirements
• Making design decisions without understanding
all the constraints on the system to be developed
results in a system which fails to meet customer’s
expectations
• Costs of correcting errors increases as the design
process advances.
• An error detected in the maintenance phase is 20
times as costly to fix as an error detected in the
coding stage.

The Basics
• A requirement mandates that something be
accomplished, transformed, produced or
provided
• Requirements engineering is the discipline
concerned with understanding the externally
imposed conditions on a proposed computer
system, determining what capabilities will meet
these imposed conditions and and documenting
those capabilities as the software requirements
for the computer system.

Requirements Engineering Process
• The processes used for RE vary widely
depending on the application domain, the
people involved and the organisation
developing the requirements
Requirements Elicitation Requirements Analysis
Requirements Specification Requirements Verification
Requirements Management
Requirements Engineering
Requirements Elicitation Requirements Analysis
Requirements Specification Requirements Verification
Requirements Management
Requirements Engineering

• Requirements elicitation : The process through which
clients and developers review, articulate and
understand the needs of the clients and the constraints
on the software
• requires involvement with the client, domain experts,
and end-users in order to establish an the client’s needs
and the constraints on the system. Here we use
techniques such as: (1) Interviews, (2) Questionnaires,
(3) Focus groups, (4) Apprenticing, and (5) modelling.

• Requirements Analysis : The process of analysing the
needs of the clients in order to arrive at a definition of
the requirements
• aims to deepen our understanding of the constraints
and client needs
• Requirements Specification : The process by which a
document is developed which clearly communicates the
requirements.
• The requirements are captured, or expressed, or
articulated, in a software requirements specification.

• Requirements Validation : The process of ensuring that
the requirements and the Software Requirements
Specification are in compliance with the needs of the
clients and the system
• techniques here include (1) reviews, inspections and
walkthroughs of requirements, and (2)prototyping.
• Requirements Management and evolution : The
planning and controlling of the requirements
engineering processes. Requirements specification
should evolve with time.

Feasibility
• Feasibility studies aim to objectively and rationally
– Uncover the strengths and weaknesses of the existing
business or proposed venture
– Opportunities and threats as presented by
the environment.
– The resources required to carry through.
– Ultimately the prospects for success of the proposition
• In its simplest term, the two criteria to judge
feasibility are cost required and value to be attained.

Types of Feasibility
• The assessment is based on an outline design of
system requirements in terms of Input, Processes,
Output, Fields, Programs, and Procedures.
• Technological feasibility
– carried out to determine whether the company has the
capability, in terms of software, hardware, personnel and
expertise, to handle the completion of the project
– when writing a feasibility report, the following should be
taken to consideration:
• A brief description of the business
• The part of the business being examined
• The human and economic factor
• The possible solutions to the problems

• Economic analysis
used method for evaluating the effectiveness of a new system. More
commonly known as cost/benefit analysis, the procedure is to determine the
benefits and savings that are expected from a candidate system and compare
them with costs. If benefits outweigh costs, then the decision is made to
design and implement the system.
Cost-based study:
It is important to identify cost and benefit factors, which can be categorized
as follows:
1. Development costs
2. Operating costs.
This is an analysis of the costs to be incurred in the system and the benefits
derivable out of the system.
Time-based study:
This is an analysis of the time required to achieve a return on investments.
The future value of a project is also a factor.

• Legal feasibility
Determines whether the proposed system conflicts with legal requirements,
e.g. data processing system must comply with the local Data Protection
Acts.
• Operational feasibility
Operational feasibility is a measure of how well a proposed system solves
the problems, and takes advantage of the opportunities identified during
scope definition and how it satisfies the requirements identified in the
requirements analysis phase of system development.
• Schedule feasibility
A project will fail if it takes too long to be completed before it is useful.
Typically this means estimating how long the system will take to develop,
and if it can be completed in a given time period using some methods
like payback period. Schedule feasibility is a measure of how
reasonable the project timetable is. You need to determine whether
the deadlines are mandatory or desirable.

• Financial feasibility
In case of a new project, financial viability can be judged on the
following parameters:
– Total estimated cost of the project
– Financing of the project in terms of its capital structure, debt equity ratio and
promoter's share of total cost
– Existing investment by the promoter in any other business
– Projected cash flow and profitability
• Other feasibility factors:
– Market and real estate feasibility
– Resource feasibility
– Cultural feasibility

• Requirements Elicitation is the process of discovering the
requirements for a system by communication with
customers, system users and others who have a stake in the
system development.
Elicitation

• The “Yes, But” syndrome
• The Undiscovered Ruins
• “User and Developer” syndrome
• “The sins of your predecessors”
Challenges of Requirements
Elicitation

The “Yes, But” syndrome
• First time users see the system the first reaction is
either, “wow this is so cool” or “Yes, but, hmmmmm,
now that I see it, what about this…? Wouldn’t it be
nice …?
• Anticipate that there will be “yes, buts” and add time
and resources to plan for feedback.
• Tends to be User Interface centric, these tend to be
the touch points of the system by the users.

The “Undiscovered Ruins”
syndrome
Teams struggle with determining when they are
done with requirements elicitation.
– Is done when all the requirements are elicited or
have they found at least enough?
– Like asking an archeologist “how many
undiscovered ruins are there?”

The “User and the developer”
syndrome
• Users do not know what
they want, or they know
what they want but
cannot articulate it.
• Users think they know
what they want until
developers give them
what they said they
wanted.
• Analysts think they
understand user
problems better than
users do.
• Recognize and appreciate
the user as domain
experts; try different
techniques.
• Provide alternative
elicitation techniques
earlier; storyboard, role
playing, prototypes, and
so on.
• Put the analyst in the
users place. Try role
playing for an hour or a
day.
CharacteristicCharacteristic ResponseResponse

The “living with the sins of your
predecessors” syndrome
• Like it or not your users (marketing) and developers
remember what happened in the past.
– Quality programs that promised things would be different.
– The last project where requirements were vague and/or
were delivered short of expectations.
• Need to build trust, slowly. Do not over commit to features,
schedule, or budget.
• Build success by delivering highest priority features early in
the process.

The Requirements Elicitation
techniques
• Interviewing and questionnaires
• Requirements workshops
• Braining Storming and idea reduction
• Use Cases
• Role Playing
• Prototyping
EX:
Summary

Interview : Context Free Question
• Goal is to prevent prejudicing the user’s response to the
questions.
• Examples:
– Who is the user?
– Who is the customer?
– Are their needs different?
– Where else can a solution to this problem be found?
• Context-free questions
• After context-free questions are asked, suggested solutions
can be explored.

Interview : Show Time
• Establish Customer or User Profile
• Assessing the Problem
• Understanding the User Environment
• Recap the Understanding
• Analyst’s Inputs on Customer’s Problems
• Assessing Your Solution (if applicable)

Technique : Requirement
workshop
• It gathers all key stakeholders together for a
short but intensely focused period.
• The use of an outside facilitator experienced
in requirements management can ensure the
success of the workshop.
• Brainstorming is the most important part of
the workshop.

Technique : Role Playing – variant
on use cases
• Role playing allows stakeholders to experience
the user’s world from the user’s perspective.
• A scripted walkthrough may replace role playing
in some situations, with the script becoming a
live storyboard.
(Class-Responsibility-Collaboration (CRC) cards,
often used in object-oriented analysis, are a
derivative of role playing.)

Requirements Analysis & Specification

Analysis & Specification
• Requirements analysis :
The process of studying and analysing the
customer and the user/stakeholder needs to arrive
at a definition of software requirements
• Requirements Specification:
o A document that clearly and precisely describes
essential requirements of software and external
interfaces (functions, performance, quality etc.)
o each requirement is specified such that its
achievement is capable of being verified by a
prescribed method like inspection, test.

Analysis of Elicitation Results
Analysis of the results of elicitation process helps to
create a better vision of the product and its
specification by:
• Explaining the problem statement better
• Marketing group establishes positioning of the
product
• Stakeholder and user summaries
o user is special case of stakeholder
o identify stakeholder w.r.t development
o identify stakeholder w.r.t system

• The precision to which Requirements are
specified is a function of
• Expertise of developers
• Knowledge developers and testers have of the
domain – the more they know, the less specific the
specification needs to be
• Access to a domain representative
• For example, in xp, requirements may be specified in
less detail but there is a customer representative on site
daily.
Requirement Specification

Requirements Perspectives
• User requirements
– Statements in natural language plus diagrams of the
services the system provides and its operational
constraints. Written for customers.
• System requirements
– A structured document setting out detailed
descriptions of the system’s functions, services and
operational constraints. Defines what should be
implemented so may be part of a contract between
client and contractor.

Types of Requirements
• Functional requirements :
Statements of services, how the system should react to
particular inputs, what functionalities is to be provided.
Functional requirements are not concerned with how these
functions are to be achieved, just what is to be achieved.
• Non – functional requirements:
deals with attributes, or properties, of the software
rather than functions. We include here aspects of the
software such as its performance, its usability, its reliability,
any safety aspects and a range of other attributes.
• Domain Requirements:
Requirements of the application domain of the system,
reflect characteristics of that domain.

Requirements Characteristics
• Unambiguous
• Testable (verifiable)
• Clear (Concise, terse, simple, precise)
• Correct
• Understandable
• Feasible
• Independent
• Atomic
• Necessary
• Implementation – free (abstract)

Requirements Characteristics
Besides the criteria for individual
requirements, 3 criteria should apply to the
set of requirements as a whole:
• Consistent
• Non redundant
• Complete

The Output
A Software Requirements Specification (SRS) – A formal
Document as the OUTPUT of the Specification stage.
it is a complete description of the behavior of a system to be
developed.
INCLUDES:
Functional Requirements
Non- Functional Requirements
Constraints
Design Strategy
Quality and Standards
Architecture
Development Methodology

Sequence Diagram
ATM Database
Card
Card number
Card OK
PIN request
PIN
Option menu
<<exception>>
invalid card
Withdraw request
Amount request
Amount
Balance request
Balance
<<exception>>
insufficient cash
Debit (amount)
Debit response
Card
Card removed
Cash
Cash removed
Receipt
Validate card
Handle request
Complete
transaction

Requirements Validation
Validation:
ensures that the software being developed will satisfy it
stakeholders
– Requirements Validation checks the software
requirements specification against stakeholders
goals and requirements
Verification:
ensures that each step followed in the process of building the soft
ware yields the right products
– Requirements Verification checks the consistency of
the software requirements specification artifacts and other
Software development products (design, implementation, ...) again
st the specification

Typical Requirements V&V
approaches
• Tracing approaches
• Prototyping
• Testing
• User manual writing
• Formal validation
• Reviews and inspections
• Walkthroughs
• Formal inspections
• Checklists

Requirements Management and Evolution

Definition
Requirements management is the process of
documenting, analyzing, tracing, prioritizing and agreeing on
requirements and then controlling change and communicating to
relevant stakeholders.
It is a continuous process throughout a project.
A requirement is a capability to which a project outcome (product
or service) should conform.

CASE Tools
IBM Rational DOORS®
Requirements management, traceability, and impact analysis
capabilities for more formal, rigorous requirements engineering
purposes, primarily suited to organizations creating manufactured
systems and products
IBM Rational Requirements Composer
Helps teams to define requirements more effectively and manage them
efficiently across the project lifecycle to gain better business outcomes
through light-weight requirements practices
IBM Rational RequisitePro®
Requirements management, traceability, and impact analysis
capabilities for project teams, primarily suited to organizations creating
application software

Software Evolution
• The priority of requirements from different
viewpoints changes during the development
process.
• System customers may specify requirements
from a business perspective that conflict with
end-user requirements.
• The business and technical environment of the
system changes during its development.

Classification for changing
requirement
• Enduring requirements. Stable requirements
derived from the core activity of the customer
organisation.
• Volatile requirements. Requirements which
change during development or when the
system is in use.

Requirements Traceability
Requirements traceability is concerned with documenting the
life of a requirement.
It should be possible to trace back to the origin of each
requirement
and
Every change made to the requirement should therefore be
documented in order to achieve traceability.
Even the use of the requirement after the implemented features
have been deployed and used should be traceable[4].

Requirement Engineering

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Requirement Engineering (20)

More from Jonathan Christian (13)

Recently uploaded (20)

Requirement Engineering