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Requirements Validation – I
Lectures # 16
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Today’s Topics
• Requirements validation
• Validation techniques
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Requirements Engineering Process
Requirements
Elicitation
Requirements
Analysis and
Negotiation
Requirements
Specification
Requirements
Validation
User Needs,
Domain Information,
Existing System
Information, Regulations,
Standards, Etc.
Requirements
Document
Agreed
Requirements
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Validation Objectives• Certifies that the requirements document is
an acceptable description of the system to
be implemented• Checks a requirements document for
– Completeness and consistency
– Conformance to standards
– Requirements conflicts
– Technical errors
– Ambiguous requirements
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Analysis and Validation• Analysis works with raw requirements as
elicited from the system stakeholders
– “Have we got the right requirements” is thekey question to be answered at this stage
• Validation works with a final draft of therequirements document i.e., with
negotiated and agreed requirements – “Have we got the requirements right” is the
key question to be answered at this stage
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Validation Inputs and Outputs
Requirements
Validation
Requirements
document
Organizational
knowledge
Organizational
standards
List of problems
Agreed actions
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Requirements Document
• Should be a complete version of the
document, not an unfinished draft.
Formatted and organized according to
organizational standards
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Organizational Knowledge• Knowledge, often implicit, of the
organization which may be used to
judge the realism of the requirements
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Organizational Standards
• Local standards e.g. for the
organization of the requirements
document
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List of Problems
• List of discovered problems in the
requirements document
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Agreed Actions• List of agreed actions in response to
requirements problems. Some
problems may have several corrective
actions; some problems may have no
associated actions
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Requirements Reviews• A group of people read and analyze the
requirements, look for problems, meet
and discuss the problems and agree on
actions to address these problems
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Requirements Review Process
Plan reviewDistribute
documents
Prepare for
review
Hold review
meeting
Follow-up
actions
Revise
documents
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Review Activities - 1• Plan review
– The review team is selected and a time and
place for the review meeting is chosen
• Distribute documents
– The requirements document is distributed to
the review team members
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Review Activities - 2
• Prepare for review
– Individual reviewers read the requirements to
find conflicts, omissions, inconsistencies,deviations from standards and other problems
• Hold review meeting
– Individual comments and problems arediscussed and a set of actions to address the
problems is agreed
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Review Activities - 3• Follow-up actions
– The chair of the review checks that the
agreed actions have been carried out
• Revise document
– The requirements document is revised
to reflect the agreed actions. At thisstage, it may be accepted or it may bere-reviewed
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Problem Actions
• Requirements clarification
• Missing information
• Requirements conflict
• Unrealistic requirement
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Requirements Clarification
• The requirement may be badly expressed ormay have accidentally omitted information
which has been collected duringrequirements elicitation
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Missing Information
• Some information is missing from the
requirements document. It is the
responsibility of the requirements
engineers who are revising the
document to discover this information
from system stakeholders
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Requirements Conflict
• There is a significant conflict betweenrequirements. The stakeholders involved
must negotiate to resolve the conflict
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Unrealistic Requirement
• The requirement does not appear to be
implement-able with the technology
available or given other constraints on
the system. Stakeholders must be
consulted to decide how to make the
requirement more realistic
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Pre-review Checking - 1• Reviews are expensive because they
involve a number of people spending time
reading and checking the requirementsdocument
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Pre-review Checking - 2
• This expense can be reduced by using pre-review checking where one person checksthe document and looks for straightforwardproblems such as missing requirements,lack of conformance to standards,typographical errors, etc.
• Document may be returned for correction orthe list of problems distributed to otherreviewers
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Pre-review Checking Stages
Check
document
structure
Check
document
completeness
Check document
against
standards
Run
automatic
checkers
Requirements
document
Problems
report
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Review Team Membership• Reviews should involve a number of
stakeholders drawn from different
backgrounds – People from different backgrounds bring
different skills and knowledge to the review
– Stakeholders feel involved in the RE process
and develop an understanding of the needs of other stakeholders
• Review team should always involve at leasta domain expert and an end-user
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Summary - 1
• Requirements validation should focus onchecking the final draft of the requirements
document for conflicts, omissions anddeviations from standards
• Inputs to the validation process are therequirements document, organizational
standards and implicit organizationalknowledge. The outputs are a list of requirements problems and agreed actions
to address these problems
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Summary - 2
• Reviews involve a group of people making
a detailed analysis of the requirements
• Review costs can be reduced by checkingthe requirements before the review for
deviations from organizational standards.
These may result from more seriousrequirements problems