Reliability and Software metrics Done by: Tayeb El Alaoui Software Engineering II Course

Outline  Introduction  Team presentation  Context presentation  Subject presentation  What is Reliability ? ( Definition from IEEE )

Outline  Difference between Errors, Faults and Failures.  Software Metrics for Reliability  Requirements Reliability Metrics.  Design and code Reliability Metrics.  Testing Reliability Metrics.  Conclusion

Introduction  Team presentation  Amine Mestari (Senior student)  Tayeb El Alaoui (Junior student)

Introduction  Context presentation  To complete the requirements of our Software Engineering II course.  To improve my communication skills.

Introduction  Subject presentation  Reliability = correctness. (For most software developers)  A better way: To go through all stages of Software lifecycle: Requirements, design and code, and Testing.

What is Reliability ?  Definition from IEEE: “The ability of a system or component to perform its required functions under stated conditions for a specified period of time."

What is Reliability ?  Three activities:  Error prevention  Fault detection and removal  Measurements to maximize Reliability

Errors, Faults and Failures  Error: programmer action or omission that results in a fault  Fault: software defect that causes a failure.  Failure: the unacceptable departure of a program operation.

Software Failure rate

Software Metrics for Reliability  The goal: To help improve the reliability of a software.  How ? To identify some potential errors from different phases of software development.

Requirements Reliability Metrics  Use: To assess individual specification statements and the vocabulary used.  How? ARM software (Automated Requirement Measurement)

Requirements Reliability Metrics (From SATC and NASA)  Lines of Text  Imperatives  Continuances  Directives  Weak Phrases  Incomplete  Options

Example of Analysis study

Design and code Reliability Metrics  Complexity (Cyclomatic)  Size  Modularity  Weighted Method per Class (WMC)

Testing Reliability Metrics  Two approaches:  Evaluation of the test plan.  Evaluation of the number of errors in the code and the rate of finding / fixing them.

Evaluation of the test plan  Use of multiple test cases  A test case contains several functions  Each function must be at least tested once.

Conclusion  Existence of Metrics to evaluate Reliability. At each phase of the development lifecycle.  The cost benefits are: factor of 14.

References  Musa, J.D., A. Iannino and K. Okumoto, Software Reliability: Measurement, Prediction, Application, Professional Edition: Software Engineering Series, McGraw–Hill, New York, NY.,  Triantafyllos, G., S. Vassiliadis and W. Kobrosly, "On the Prediction of Computer Implementation Faults Via Static Error Prediction Models," Journal of Systems and Software, Vol. 28, No. 2, February 1995, pp  Rosenberg, L., and Hammer, T., Metrics for Quality Assurance and Risk Assessment, Proc. Eleventh International Software Quality Week, San Francisco, CA,  Hammer, T., Rosenberg, L., Huffman, L., Hyatt, L., Measuring Requirements Testing in Proc. International Conference on Software Engineering (Boston MA, May 1997) IEEE Computer Society Press.