16-11-2012, 03:42 PM
Software Quality Management
[attachment=39812]
De nition:
1. Conformance to speci cation: Quality that
is de ned as a matter of products and ser-
vices whose measurable characteristics satisfy
a xed speci cation that is conformance to an
in beforehand de ned speci cation.
2. Meeting customer needs: Quality that is iden-
ti ed independent of any measurable charac-
teristics. That is quality is de ned as the
products or services capability to meet cus-
tomer expectations explicit or not.
3. Quality is the degree of goodness of a product
or service or perceived by the customer.
The Department of Defense (DOD, 1985) in the
USA de nes software quality as \ the degree to
which the attributes of the software enable it to
perform its intended end use" .
HIERARCHICAL MODEL OF QUALITY
To compare quality in di erent situations, both
qualitatively and quantitatively, it is necessary to
establish a model of quality.
Many model suggested for quality.
Most are hierarchical in nature.
A quantitative assessment is generally made, along
with a more quanti ed assessment.
Two principal models of this type, one by Boehm(1978)
and one byMcCall in 1977. A hierarchical model
of software quality is based upon a set of quality
criteria, each of which has a set of measures or
metrics associated with it.
The issues relating to the criteria of quality are:
What criteria of quality should be employed?
How do they inter-relate?
How may the associated metrics be combined
into a meaningful overall measure of Quality?
The Boehm model (1978)
It is to provide a set of well-de ned, well-
di erentiated characteristics of software qual-
ity.
It is hierarchical in nature but the hierarchy
is extended, so that quality criteria are sub-
divided.
According to the uses made of the system and
they are classed into general or as is and the
utilities are a subtype of the general utilities,
to the product operation.
There are two levels of actual quality criteria,
the intermediate level being further split into
primitive characteristics which are amenable
to measurement.
This model is based upon a much larger set
of criteria than McCall s model, but retains
the same emphasis on technical criteria.
The two models share a number of common
characteristics are,
Quality Models
In the previous section we presented some quality management gurus
as well as their ideas and views on quality primarily because this is
a used and appreciated approach for dealing with quality issues in
software developing organizations. Whereas the quality management
philosophies presented represent a more
exible and qualitative view
on quality, this section will present a more xed and quantitative
quality structure view
McCalls Quality Model (1977)
One of the more renown predecessors of todays quality models is the
quality model presented by Jim McCall (also known as the General
Electrics Model of 1977). This model, as well as other contemporary
models, originates from the US military (it was developed for the
US Air Force, promoted within DoD) and is primarily aimed towards
the system developers and the system development process. It his
quality model McCall attempts to bridge the gap between users and
developers by focusing on a number of software quality factor that
re
ect both the users views and the developers priorities.
Boehms Quality Model (1978)
The second of the basic and founding predeces-
sors of todays quality models is the quality model
presented by Barry W. Boehm . Boehm addresses
the contemporary shortcomings of models that
automatically and quantitatively evaluate the qual-
ity of software. In essence his models attempts
to qualitatively de ne software quality by a given
set of attributes and metrics. Boehm's model is
similar to the McCall Quality Model in that it
also presents a hierarchical quality model struc-
tured around high-level characteristics, interme-
diate level characteristics, primitive characteris-
tics - each of which contributes to the overall
quality level.
QUALITY CRITERIA and INTERRELATION
The individual measure of software quality pro-
vided do not provide an over all measure of soft-
ware quality. The individual measures must be
combined. The individual measures of quality
may con
ict with each other.
Some of these relationships are described below;
Integrity vs. eciency (inverse) the control
of access to data or software requires addi-
tional code and processing leading to a longer
runtime and additional storage requirement.
Usability vs. eciency (inverse) Improvements
in the human / computer interface may signif-
icantly increase the amount of code and power
required.
Maintainability and testability vs. eciency
(inverse) Optimized and compact code is not
easy to maintain.
Portability vs. eciency (inverse) the use
of optimized software or system utilities will
lead to decrease in probability.
[attachment=39812]
De nition:
1. Conformance to speci cation: Quality that
is de ned as a matter of products and ser-
vices whose measurable characteristics satisfy
a xed speci cation that is conformance to an
in beforehand de ned speci cation.
2. Meeting customer needs: Quality that is iden-
ti ed independent of any measurable charac-
teristics. That is quality is de ned as the
products or services capability to meet cus-
tomer expectations explicit or not.
3. Quality is the degree of goodness of a product
or service or perceived by the customer.
The Department of Defense (DOD, 1985) in the
USA de nes software quality as \ the degree to
which the attributes of the software enable it to
perform its intended end use" .
HIERARCHICAL MODEL OF QUALITY
To compare quality in di erent situations, both
qualitatively and quantitatively, it is necessary to
establish a model of quality.
Many model suggested for quality.
Most are hierarchical in nature.
A quantitative assessment is generally made, along
with a more quanti ed assessment.
Two principal models of this type, one by Boehm(1978)
and one byMcCall in 1977. A hierarchical model
of software quality is based upon a set of quality
criteria, each of which has a set of measures or
metrics associated with it.
The issues relating to the criteria of quality are:
What criteria of quality should be employed?
How do they inter-relate?
How may the associated metrics be combined
into a meaningful overall measure of Quality?
The Boehm model (1978)
It is to provide a set of well-de ned, well-
di erentiated characteristics of software qual-
ity.
It is hierarchical in nature but the hierarchy
is extended, so that quality criteria are sub-
divided.
According to the uses made of the system and
they are classed into general or as is and the
utilities are a subtype of the general utilities,
to the product operation.
There are two levels of actual quality criteria,
the intermediate level being further split into
primitive characteristics which are amenable
to measurement.
This model is based upon a much larger set
of criteria than McCall s model, but retains
the same emphasis on technical criteria.
The two models share a number of common
characteristics are,
Quality Models
In the previous section we presented some quality management gurus
as well as their ideas and views on quality primarily because this is
a used and appreciated approach for dealing with quality issues in
software developing organizations. Whereas the quality management
philosophies presented represent a more
exible and qualitative view
on quality, this section will present a more xed and quantitative
quality structure view
McCalls Quality Model (1977)
One of the more renown predecessors of todays quality models is the
quality model presented by Jim McCall (also known as the General
Electrics Model of 1977). This model, as well as other contemporary
models, originates from the US military (it was developed for the
US Air Force, promoted within DoD) and is primarily aimed towards
the system developers and the system development process. It his
quality model McCall attempts to bridge the gap between users and
developers by focusing on a number of software quality factor that
re
ect both the users views and the developers priorities.
Boehms Quality Model (1978)
The second of the basic and founding predeces-
sors of todays quality models is the quality model
presented by Barry W. Boehm . Boehm addresses
the contemporary shortcomings of models that
automatically and quantitatively evaluate the qual-
ity of software. In essence his models attempts
to qualitatively de ne software quality by a given
set of attributes and metrics. Boehm's model is
similar to the McCall Quality Model in that it
also presents a hierarchical quality model struc-
tured around high-level characteristics, interme-
diate level characteristics, primitive characteris-
tics - each of which contributes to the overall
quality level.
QUALITY CRITERIA and INTERRELATION
The individual measure of software quality pro-
vided do not provide an over all measure of soft-
ware quality. The individual measures must be
combined. The individual measures of quality
may con
ict with each other.
Some of these relationships are described below;
Integrity vs. eciency (inverse) the control
of access to data or software requires addi-
tional code and processing leading to a longer
runtime and additional storage requirement.
Usability vs. eciency (inverse) Improvements
in the human / computer interface may signif-
icantly increase the amount of code and power
required.
Maintainability and testability vs. eciency
(inverse) Optimized and compact code is not
easy to maintain.
Portability vs. eciency (inverse) the use
of optimized software or system utilities will
lead to decrease in probability.