Measurement and Metrics - Requirements Engineering and Management for Software Development Projects - page 135

practitioners with each claiming that their standard as the right one and all others
are aberrations. Hence, if I do not define what I mean by the terms used in this
book, it is possible that I may aggrieve/mislead some. Therefore, I would like to
define the terms used in this topic. Let us examine some popular definitions for
popular terms used in the software development in the context of measurement and
benchmarking.
Let us look at measurement first and then at metric.
Measurement
CMMI model document version 1.3 defines the term ''measure'' first. It defines
measure as ''a variable to which a value is assigned as a result of measurement''.
CMMI model document goes on to distinguish ''measure'' as ''base measure'' and
as ''derived measure.'' CMMI defines base measure as ''A base measure is
functionally independent of other measures.'' CMMI defines derived measure as
''Measure that is defined as a function of two or more values of base measures.'' It
defines ''measurement'' as ''A set of operations to determine the value of a
measure'' and the measurement result as ''a value determined by performing
measurement.''
From these definitions, we can, for our context, infer that:
1. Measurement is a process to determine the numerical value of some aspect of
software development.
2. The result of measurement is a ''measure'' in numerical terms.
3. Base measure is the direct result of measurement.
4. We need to perform some mathematical transformations on one or more
measures to obtain the ''derived measure''.
Metric—IEEE standard 610 Standard Glossary of Software Engineering
Terminology defines metric as ''A quantitative measure of the degree to which a
system, component or process possesses a given attribute'' and ''quality metric'' as
''A quantitative measure of the degree to which an item possesses a given quality
attribute'' and ''A function whose inputs are software data and whose output is a
single numerical value that can be interpreted as the degree to which the software
possesses a given quality attribute.'' CMMI model document version 1.3 used the
term ''metric'' at a few places but left it undefined.
From the first IEEE definition of metric, we can see that it is very similar to the
definition of base measure given by the CMMI model document. The second defi-
nition of IEEE for the ''quality metric'' is again, very similar to the CMMI definition
of the ''derived measure.''
It would have been great if both (IEEE and CMMI) had agreed on a common
set of terminology and definitions. It seems to me that the authors of CMMI
wanted to move away from the oft used term ''metric'' and used the term ''derived
measure.'' Still, they used the term ''metric'' a few times in their model document
version 1.3. That shows the popularity of the term ''metric'' in the software
development fraternity.
For the purpose of this topic, I am going to use the two terms, measurement, and
metric.