Error Tracking
• Defect removal efficiency
– DRE = E / (E+D)
• E – errors found before shipment
• D – errors found during operation
– Provides strong indication of the effectiveness of
the quality assurance activities
• Track errors in work products (requirement
specifications, design documents, source code etc) to
assess the status of a project
• Collect error related metrics over many projects
Recap
Software Engineering II
Lecture 26
Fakhar Lodhi
Using Error Tracking to assess
progress
• Let us assume that we have collected errors and
defect data over the last 24 months
– Errors per requirement specification page – Ereq
– Error per component – design level – Edesign
– Errors per component – code level – Ecode
– DRE – requirement analysis
– DRE – architectural design
– DRE – coding
Using Error Tracking to assess
progress
• Record the number of errors found during each SE
step
• Calculate current values for Ereq, Edesign, and Ecode
• Compare to averages of past projects
• If the current results vary more than 20% from
average, there may be cause for concern and there is
certainly cause for investigation
Example
• Ereq for the current project = 2.1
• Organizational average = 3.6
• Can also be used to better target review and/or
testing resources
– 120 components
– 32 exhibit Edesign > 1.2 average
– Adjust code review resources accordingly
Software Quality
• Software quality is defined as:
– Conformance to explicitly stated functional and
non-functional requirements, explicitly
documented development standards, and implicit
characteristics that are expected of all
professionally developed software.
Software Quality
• 3 important points
– Software requirements are the foundation from
which quality is measured. Lack of conformance is
lack of quality
– Specified standards define a set of development
criteria that guide the manner in which software is
engineered. If the criteria are not followed, lack of
quality will almost surely result.
– A set of implicit requirements often goes
unmentioned (ease of use, good maintainability
etc.)
Quality Assurance
• Goal is to provide the management with the
necessary data to be informed about product quality
• Consists of auditing and reporting functions of
management
• If data provided through QA identifies problems, the
management deploys the necessary resources to fix
it