Writing Better Requirements

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Writing Better Requirements

• Gordon Woods
• Independent Consultant
• gordon_at_cigitech.demon.co.uk

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Requirement Construction

• The Subject/Noun shall verb at/when/during
  object/quantity adverb condition/object.

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Requirement Construction
What?
When?
Action

• conduct
• command
• perform
• compute
• launch
• obtain
• provide
• sustain
• interoperate with

• the steering rate
• Target Flight data
• the wind speed
• the error message
• WMD
• the launcher to position
• other systems

• Within 1 hour
• within 45 mins
• every frame
• up to 60 knots

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The path to linguistic happiness...
PIE
OR
3.1426...
The cow and the deer both eat at the same table
but neither can understand the other.
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Types of Requirements

• Functional
• Non Functional
• Interface
• Performance
• Constraint
• Quality and the ilities
• Safety
• Derived
• Behavioural
• Operational

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Defects to avoid

• Optionality

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Some forms of IMINT shall be available to
infantry and RM company headquarters.
The system shall not be operated solely by mouse
(or other pointing device) or solely by the
keyboard. The input methods shall be under user
control.
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Defects to avoid

• Optionality
• Vagueness

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The system shall be capable of providing the
required level of operational capability at all
times.
The User shall be able to utilise an air system
that is airworthy and meets all appropriate
regulations, both military and civilian, at all
times.
xxxx shall distribute other relevant tactical
data amongst yyyy units.
xxxx shall be able to sustain extended duration
operations with low logistic and training
demands.
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Defects to avoid

• Optionality
• Vagueness
• Weakness

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xxxx should be capable of being refuelled in
flight over the widest height range.
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Defects to avoid

• Optionality
• Vagueness
• Weakness
• Over specification

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The User shall be able to be deployable "World
Wide " .
The user shall be able to fulfil the mission
requirements.
The User shall be able to refuel the xxxx in
flight.
The fuel flow shall be less than xx m/s.
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Defects to avoid

• Optionality
• Vagueness
• Weakness
• Over specification
• Subjectivity

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To maximise operator safety the User shall be
able to conduct operations with all minesweeping
components of xxx in an unmanned state.
The degradation of ESM performance by the
introduction of xxxx shall be minimised.
The user shall be provided with an xxxx
capability that minimises harmful effects to the
environment.
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Defects to avoid

• Optionality
• Vagueness
• Weakness
• Over specification
• Subjectivity
• Multiplicity

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The system shall provide the capability for the
Authority's nominated personel to flag a work
flow task as 'on hold' and record the reasons why
it has been put on hold. Other users working on
the same workflow, who have workflow tasks that
are allocated for execution but not yet
completed, shall be notified that a user has put
a workflow task on hold and shall be able to view
the reasons why, but they shall not be prevented
from continuing their allocated workflow tasks
should they consider it appropriate to do so.
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Defects to avoid

• Optionality
• Vagueness
• Weakness
• Over specification
• Subjectivity
• Multiplicity
• Unclear meaning

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xxxx must be spectrally efficient.
xxxx must provide a data backbone with defined
limits of latency.
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Defects to avoid

• Optionality
• Vagueness
• Weakness
• Over specification
• Subjectivity
• Multiplicity
• Unclear meaning
• Implicit meaning

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The inert weapon shall have the same lives as
the operational weapon.
xxxx equipment must be allocated on the basis of
MoD's priorities.
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Finally...
The xxx shall provide a coercive influence
through the significant psychological impact
afforded by a warlike appearance.
S
S
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Attributes

• Effectiveness Envelope
• Acceptance Criteria
• Justification
• Rationale
• Remarks
• Source Document
• Derivation

• Keywords
• Priority
• Cost
• Risk
• Stakeholder
• Owner
• Urgency

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Verifiable

• Definition
• Can the requirement be quantified?
• Can the Requirement be Accepted
• Effectiveness Envelope or Performance
  Requirements
• Can it be tested? (quantitatively)
• Direct Measurement
• Demonstration/Observation
• Analysis
• Modelling

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Attainable

• Implementation free
• Achievable?
• Performance Cost Time Technical Constraints
• Risks
• Realistic Technology
• Kano Model

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Kano Model
Satisfied
Exciting
Expected
Present
Not Present
Basic
Not Satisfied
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Attainable

• Implementation free
• Achievable?
• Performance Cost Time Technical Constraints
• Risks
• Realistic Technology
• Kano Model

• Trade offs
• Interoperability

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Complete and Concise

• No TBD
• -gt TBC
• No reliance on other requirements or headings
• Simple statement
• Positive language
• Neither and nor or

• No bullets

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Unambiguous

• Is the meaning clear
• Can it be misinterpreted?
• Understandable
• Defined Terms/Definitions/Acronyms
• No banned words

A beautiful tree can bear forth bitter fruit.
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Some Banned Words

• adequate
• applicable
• appropriate
• approximate
• bad
• best practice
• between
• clearly
• compatible
• completely

• consider
• could
• down to
• easy/easily
• effective
• efficient
• equivalent
• excellent
• good
• his/her

• however
• ideal
• ie eg etc
• in order to
• include but shall not be limited to
• least
• like
• low
• maximise
• may

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Some More Banned Words

• sufficient
• suitable
• support
• target
• typical
• up to
• user friendly
• whether
• will
• with
• worse

• most
• minimum/mal
• must
• nearly
• necessary
• needed
• normal
• or
• possible/bly
• practicable
• provide

• quality
• readily
• relevant
• safe/ly
• same
• should
• significant
• similar
• so as
• subject to
• substantial

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Unique

• Identification
• Consistent
• No duplications or redundancy
• No conflicts
• Structured environment
• Nodes v Tips
• Levels
• Pigeon holes

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Managed

• Whole life cycle management
• Priority KUR/KSR
• Traceability
• Satisfies (nm)
• Complies with (nm)
• Contributes to (nm)
• Establishes (11)

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Managed (2)

• Review
• Peer
• Specialist
• Stakeholder

Requirements Working Group

• Modifiable (minimal interdependencies)
• Changes
• Status recorded
• Audit trail

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Managed (3)

• Maturity
• Requirements are not just for Concept
• Metrics
• End date driven

The anxious farmer who brings his crops to market
too early, before they had a chance to ripen, may
leave with them unsold.
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Managed (4)

• Mitigation
• Involve ALL stakeholders
• Review Gates
• Decision points
• Realistic Programme
• Personnel Training

• Risks
• Changes to goalposts
• Cost cuts
• Technical problems
• Programme slippage
• Personnel changes
• Tradeoffs

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Managed (5)

• Incremental delivery
• Baselines
• CONEMP/CONUSE/CONOPS

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• CONEMP
• for a specific capability within a range of
  operations or scenarios.
• CONUSE
• A developed CONEMP (after MG before ISD). The
  way in which specific equipment is to be used in
  a range of operations or scenarios.
• CONOPS
• How a range of different capabilities or
  equipment is used in an operational context.
  Extant and Future capabilities.

Taken from The Provenance, Authority and
Coherence of Concepts, Feb 2003
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Help with writing better requirements

• Syntactic Analysis Tools

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Syntactic Analysis Tools

• QuARS
• Quality Analyzer of Requirements Specification
• FRED
• First Requirements Elucidator Demonstration

Figure Of Merit 100 (1 - number of defects /
number of requirements).

• TIGER
• Tool to InGest and Elucidate Requirements
• ARM
• Automated Requirement Measurement Tool

http//www.secoe.org/
http//satc.gsfc.nasa.gov/tools/arm/
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Help with writing better requirements

• Syntactic Analysis Tools

• DOORS Add on Tools

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DOORS Add on Tools

• Cogent Defence and Security Networks
• defence_at_cogent-dsn.com
• Scenario Plus
• http//www.scenarioplus.org.uk/

You travel on the land by marching and on the
river by rowing. Do not try to march on the
river or you will surely drown.
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Help with writing better requirements

• Syntactic Analysis Tools
• DOORS Add on Tools

• Checklists

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Checklists
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Help with writing better requirements

• Syntactic Analysis Tools
• DOORS Add on Tools
• Checklists

• Alternative methods to writing words

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Alternative methods to writing

• Entity Relationship Diagrams
• Goal based methods
• Scenarios and Use Cases
• Architectural Frameworks

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Summary

• Verifiable
• Attainable
• Complete and Concise
• Unambiguous
• Unique
• Managed

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Further information

• BCS RESG
• http//www.resg.org.uk
• DPA Requirements Managers
• http//y4.dpa.r.mil.uk/kb/Community/ReqtsMngt/inde
  x.htm
• Scenario Plus
• http//www.scenarioplus.org.uk
• Ivy Hooks - Compliance Automation
• http//www.complianceautomation.com
• Atlantic Systems Guild
• http//www.systemsguild.com

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Questions ?