Lecture Systems analysis and design with UML (3 e) Chapter 4 Requirements determination

Chapter 4:
Requirements Determination

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Objectives
• Understand how to create a requirements
definition.
• Become familiar with requirements analysis
techniques.
• Understand when to use each requirements
analysis technique.
• Understand how to gather requirements using
interviews, JAD sessions, questionnaires,
document analysis, and observation.
• Understand when to use each requirementsgathering technique.
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The SDLC and Requirements
• The SDLC transforms the existing (as is)
system into the proposed (to be) system
• Requirements determination step is the single
most critical step of the entire SDLC
– Studies show that more than half of all system
failures are due to problems with requirements

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REQUIREMENTS DETERMINATION
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Defining a Requirement
• A statement of what the system must do or
what characteristic it must have
• During analysis, requirements are written
from the perspective of the businessperson
• Two kinds of requirements:
– Functional
– Nonfunctional

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Nonfunctional Requirements

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Requirements Definition Report
•
•

•
•
•
•
•
•

Correct
Unambiguous
Complete
Consistent
Verifiable
Modifiable
Traceable
Ranked for importance
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A Bad Requirement
Initial
Initial Specification:
Specification: Software
Software will
will not
not be
be loaded
loaded from
from unknown
unknown

sources
sources onto
onto the
the system
system without
without first
first having
having the
the software
software tested
tested and
and
approved.
approved.
Critique:
Critique:
•• Ambiguous
Ambiguous –– ifif the
the software
software is
is tested
tested and
and approved,
approved, can
can itit be
be
loaded
loaded from
from unknown
unknown sources?

sources?
•• (not)
(not) Testable
Testable –– itit is
is stated
stated as
as aa negative
negative requirement
requirement making
making itit
difficult
difficult to
to verify.
verify.
•• (not)
(not) Traceable
Traceable –– aa unique
unique identifier
identifier is
is missing.
missing.
Re-specification:
Re-specification: 3.4.5.2
3.4.5.2 Software
Software shall
shall be
be loaded
loaded onto
onto the
the operational

operational
system
system only
only after
after itit has
has been
been tested
tested and
and approved.
approved.
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Determining Requirements
• Requirements are best determined by
systems analysts and business people
together
• Techniques available to the systems analyst:
– Interviews
– Questionnaires
– Observation
– Joint application development (JAD)
– Document analysis
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REQUIREMENTS ANALYSIS
STRATEGIES

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Requirements Analysis Strategies
• The basic process of analysis is divided into:
1. Understanding the as-is system
2. Identifying improvements
3. Developing requirements for the to-be system

• There are 3 requirements analysis strategies
1. Business process automation
2. Business process improvement
3. Business process reengineering
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Business Process Automation
• BPA leaves the basic way in which the
organization operates unchanged and uses
computer technology to do some of the work
• Low risk, but low payoff
• Planners in BPA projects invest significant
time in understanding the as-is system using:
– Problem analysis
– Root cause analysis
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Problem Analysis
• Users and managers identify problems with
the as-is system and describe how to solve
them in the to-be system
• Tends to solve problems rather than capitalize
on opportunities
• Improvements tend to be small and
incremental

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Root Cause Analysis
• Users are not asked for solutions, but for:
– A list of (prioritized) problems
– All possible root causes for those problems

• Analysts investigate each root cause to find:
– Solutions for the highest priority problems
– Root causes that are common to multiple
problems

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Root Cause Analysis Example

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Business Process Improvement
• BPI makes moderate changes to the way in
which the organization operates to take
advantage of new opportunities offered by
technology or to copy what competitors are
doing
• Common activities:
– Duration analysis
– Activity-based costing
– Informal benchmarking
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Business Process Reengineering
• BPR changes the fundamental way in which
the organization operates
• Spends little time understanding the as-is,
because their goal is to focus on new ideas
and new ways of doing business
• Popular activities:
– Outcome analysis
– Technology analysis
– Activity elimination
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Selecting the Appropriate Strategies

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REQUIREMENTS-GATHERING
TECHNIQUES
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Five Basic Steps of Interviews
•
•
•
•
•

Slide 20

Selecting interviewees
Designing interview questions
Preparing for the interview
Conducting the interview
Post-interview follow-up

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Selecting Interviewees
• Based on information needed
• Often good to get different perspectives
– Managers
– Users
– Ideally, all key stakeholders

Slide 21

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Interviewing Strategies
Top-down
High-level:
Very general

How
can order
processing be
improved?

How can we reduce the
Medium-level:
Moderately specific number of times that customers
return ordered items?

Low-level:
Very specific

How can we reduce the number of
errors in order processing (e.g., shipping
the wrong products)?

Bottom-up

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Post-Interview

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Joint Application Development
• Allows the project team, users, and
management to work together to identify
requirements for the system
• Often the most useful method for collecting
information from users
• Key roles:
– Facilitator
– Scribe
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JAD Meeting Room

JPEG Figure 5-5 Goes Here

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