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Requirements Traceability
Lecture # 20
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Recap of Last Two Lectures
We talked about different aspects of
requirements management, i.e.,
managing the changes in requirements
in detail
Requirements cannot be managedproperly if requirements traceability is
not implemented
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Requirements Traceability
Refers to ability to describe and follow the
life of a requirement, in both a forwards and
backwards direction
That is from its origins, through its
development and specification, to its
subsequent deployment and use, andthrough all periods of on-going refinement
and iteration in any of these phases
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Tracing Requirements
It is important to trace requirements
both ways
Origin of a requirement
How is it implemented
This is a continuous process
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Classifications of Requirements
Traceability Backward-from traceability
Forward-from traceability Backward-to traceability
Forward-to traceability
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Backward-from Traceability
Links requirements to their sources in
other documents or people
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Forward-from Traceability
Links requirements to design and
implementation components
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Backward-to Traceability
Links design and implementation
components back to requirements
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Forward-to Traceability
Links other documents (which may
have preceded the requirements
document) to relevant requirements
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Backwards and Forwards
Traceability
Business plan Requirements document Design specification
Forward-to traceability Forward-from traceability
Backward-from traceability Backward-to traceability
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Categories of Traceability
Requirements-sources traceability
Requirements-rationale traceability
Requirements-requirementstraceability
Requirements-architecture traceability
Requirements-design traceability
Requirements-interface traceability
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Requirements-Sources
Traceability Links the requirement and the people
or documents which specified the
requirement
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Requirements-Rationale
Traceability Links the requirement with a
description of why that requirement
has been specified. This can be a
distillation of information from several
sources
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Requirements-Requirements
Traceability Links requirements with other
requirements which are, in some way,
dependent on them. This should be a
two-way link (dependent on them and
is-dependent on)
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Requirements-Architecture
Traceability Links requirements with the sub-
systems where these requirements are
implemented. This is particularly
important where sub-systems are being
developed by different sub-contractors
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Requirements-Design
Traceability Links requirements with specific
hardware or software components in
the system, which are used to
implement the requirement
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Requirements-Interface
Traceability Links requirements with the interfaces
of external systems, which are used in
the provision of the requirements
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Traceability Tables
Requirements traceability information
can be kept in traceability tables, each
table relating requirements to one or
more aspects of the system or its
environment
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A Generic Traceability Table
A01 A02 A03 Aii
R01
R02
R03
Rnn
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Need for Traceability Policy
Huge amount of information, which is
expensive to collect, analyze, and
update
Need to continuously update
traceability information A traceability policy is needed
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Traceability Policy
Traceability information
Traceability techniques
When to collect information
Roles
Documentation of policy exceptions
Process of managing information
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Traceability Information
No. of requirements
Estimated lifetime
Level of organizations maturity
Project team and composition
Type of system
Specific customer requirements
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Basic Types of Requirements
Traceability - 1 Pre-RS traceability
Concerned with those aspects of a
requirements life prior to its inclusion in theRS (requirements production)
Post-RS traceability
Concerned with those aspects of arequirements life that result from its inclusion
in the RS (requirements deployment)
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Pre-RS Traceability
Depends on the ability to trace requirementsfrom and back to, their originating
statements, through the process ofrequirements production and refinement, inwhich statements from diverse sources areeventually integrated into a single
requirement in the RS Changes in the process need to be re-
worked into the RS
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Post-RS Traceability
Depends on the ability to trace
requirements from, and back to, a
baseline (the RS), through a succession
of artifacts in which they are
distributed
Changes to the baseline need to be re-
propagated through this chain
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Pre-RS Traceability and
Rationale Mostly only Post-RS traceability is
considered sufficient
Pre-RS traceability captures the
rationale for each requirement, which
is a very important aspect in managingrequirements properly
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Summary
Requirements traceability is an on-goingprocess, and has two basic types: pre-RSand post-RS
There are four classifications ofrequirements traceability
We discussed traceability information,
policies, and techniques Without proper traceability, requirements
cannot be managed
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References
Software Engineering: A PractitionersApproach by R. Pressman, PH 2000
Requirements Engineering: Processes andTechniques by G. Kotonya and I.Sommerville, John Wiley & Sons, 1998
An Analysis of the RequirementsTraceability Problem, O.C.Z. Gotel &A.C.W. Finkelstein, TR-93-41, ImperialCollege, London, UK