06-12-2012, 01:45 PM
Software Metrics
1Software Metrics.ppt (Size: 282.5 KB / Downloads: 36)
Lecture Objectives
To understand the importance of measurement in software engineering
To describe and compare the different metrics that can be used for measuring software
To understand the important factors that affect the measurement of software
Why Do We Measure?
To indicate the quality of the product
To assess the productivity of the people who produce the product
To assess the benefits derived from new software engineering methods and tools
To form a baseline for estimation
To help justify requests for new tools or additional training
Definitions
Measure - quantitative indication of the extent, amount, dimension, capacity, or size of some attribute of a product or process.
Measurement - the act of determining a measure
Metric - a quantitative measure of the degree to which a system, component, or process possesses a given attribute (IEEE)
What Can Be Measured?
Direct measures
Lines of codes (LOC), speed, cost, memory size, errors, ...
Indirect measures
Quality, functionality, complexity, reliability, efficiency, maintainability,
Example: length of a pipe is a direct measure.
the quality of the pipes can only be measured indirectly by finding the ratio of the accepted pipes to the rejected.
Size-Oriented Metrics
Based on the “size” of the software produced.
Project data measured, including cost and effort, pages, defects…etc.
Mainly uses the LOC as the normalization value.
Advantages: easily counted, large body of literature and data based on LOC
Disadvantages: language dependent, programmer dependent.
Useful for projects with similar environment.
Therefore, size-oriented metrics are not universally accepted as the best way to measure the software process.
Software information domain values
Number of user inputs: user inputs.
Number of user outputs: reports, screens, error messages, etc.
Number of user inquiries: an on-line input that generates an immediate on-line output response.
Number of files: each logical (logical grouping of data) master file is counted.
Number of external interfaces: all machine readable interfaces (e.g. data files on some storage media) that are used to transmit information to another system are counted.