Error Tracking Defect removal efficiency DRE E ED

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