Page 79 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Unit 4: Introduction to Validation, Metrics

quality assurance systems the common software metrics that are checked for improvement are Notes
the Source lines of code, cyclical complexity of the code, Function point analysis, bugs per line
of code, code coverage, number of classes and interfaces, cohesion and coupling between the
modules etc.
Common software metrics include:
• Bugs per line of code

• Code coverage
• Cohesion
• Coupling
• Cyclomatic complexity

• Function point analysis
• Number of classes and interfaces

• Number of lines of customer requirements
• Order of growth
• Source lines of code
• Robert Cecil Martin’s software package metrics

Software Quality Metrics focus on the process, project and product. By analyzing the metrics
the organization the organization can take corrective action to fix those areas in the process,
project or product which are the cause of the software defects.
The de-facto definition of software quality consists of the two major attributes based on intrinsic
product quality and the user acceptability. The software quality metric encapsulates the two
attributes, addressing the mean time to failure and defect density within the software components.
Finally it assesses user requirements and acceptability of the software. The intrinsic quality of
a software product is generally measured by the number of functional defects in the software,
often referred to as bugs, or by testing the software in run time mode for inherent vulnerability
to determine the software “crash” scenarios. In operational terms, the two metrics are often
described by terms namely the defect density (rate) and mean time to failure (MTTF).

Although there are many measures of software quality, correctness, maintainability, integrity
and usability provide useful insight.

Correctness
A program must operate correctly. Correctness is the degree to which the software performs the
required functions accurately. One of the most common measures is Defects per KLOC. KLOC
means thousands (Kilo) Of Lines of Code.) KLOC is a way of measuring the size of a computer
program by counting the number of lines of source code a program has.
Maintainability
Maintainability is the ease with which a program can be correct if an error occurs. Since there is
no direct way of measuring this indirect way has been used to measure this. MTTC (Mean time
to change) is one such measure. It measures when a error is found, how much time it takes to
analyze the change, design the modification, implement it and test it.
Integrity

This measure the system’s ability to with stand attacks to its security. In order to measure
integrity two additional parameters are threat and security need to be defined.

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