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'Quality' is a relative term and it is generally
used with reference to the end use of the product. The word 'quality'
has variety of meanings including fitness for purpose, grade, degree
of preference, degree of excellence & fulfillment of promises.
It may also be defined as a degree of conformance of design and
specifications. American Heritage Dictionary defines Quality as
"A characteristics or attribute of something". When we
examine an item based on its measurable characteristics, two kinds
of quality may be encountered:
1.Quality of design
2.Quality of conformance
The quality of design of a product is concerned with the tightness
of the specifications for manufacture of the product. It depends
on the type of customers in the market, capital goods, profit consideration
of the organization & special requirements of the product. The
quality of conformance is concerned with how well the manufactured
product conforms to the quality of design. To achieve this, the
incoming raw materials have to be of adequate quality, selection
of the process should be proper, operators need to be trained and
experienced & proper care should be taken during shipment and
storage of finished goods. A proper inspection program & feedback
mechanism should exist, both for internal inspection & for the
customers.
The quality of performance is concerned with how well the manufactured
product gives its performance t depends upon the quality of design
& the quality of conformance.
The cost of carrying out the company's quality functions (meeting
the quality needs of the customers) are known as costs of quality.
It provides baseline for the current cost of quality and identifies
opportunities for reducing the cost of quality in the future. A
quality cost committee of the American Society for Quality Control
has recommended that quality cost be defined in four categories:
1.Cost of prevention
2.Cost of appraisal
3.Cost of internal failures
4.Cost of external failures
Total Quality Management
Kaizen - develop a process that is visible,
repeatable, and measurable
Atarimae hinshitsu - examine the intangibles that affect
the process and work to optimize their impact on the process
Kansei - examine the way the product is used by the customer
with an eye to improving both the product and the development process
Miryokuteki hinshitsu - observe product use in the market
place to uncover new product applications and identify new products
to develop
Quality Control
Quality control involves series of inspections, reviews,
and tests used to ensure conformance of a work product to its specifications.
Quality control includes a feedback loop to the process that created
the work product.
As per A. Y. Feigorbaum Total Quality Control is:
" An effective system for integrating the quality development,
quality maintenance & quality improvement efforts of the various
groups in an organization, so as to enable production and services
at the most economical levels which allows full customer satisfaction"
Software quality characteristics
- Functionality (including precision)
- Reliability
- Efficiency
- Operability
- Maintainability
- Portability qualities desired by the users
- Mean time to failure (MTTF)
- Response time
- Defect rates
- Repair expenses
Peculiarities of Software
Software can include not only "instructions for
computers", but the corresponding "instructions for humans"
such as education courses, procedures, or theses.
High Quality Software can defined as: "Software that ensures
precision in numeric calculations, performs high-speed transition
processing, ensures extremely long mean time failures (MTTF), ensures
uninterrupted operation despite hardware failures, ensures error-free
executions of functions (within a limited range)."
Quality software is reasonably bug-free, delivered on time and within
budget, meets requirements and/or expectations, and is maintainable.
However, quality is obviously a subjective term. It will depend
on who the 'customer' is and their overall influence in the scheme
of things. A wide-angle view of the 'customers' of a software development
project might include end-users, customer acceptance testers, customer
contract officers, customer management, the development organization's
management/ accountants/ testers/ salespeople, future software maintenance
engineers, stockholders, magazine columnists, etc. Each type of
'customer' will have their own slant on 'quality' - the accounting
department might define quality in terms of profits while an end-user
might define quality as user-friendly and bug-free.
Various Standards for Software Quality
Standards are documented agreements containing technical
specifications or other precise criteria to be used consistently
as rules ,guidelines or definitions of characteristics , to ensure
that materials ,products,processes and services are fit for their
purpose. Prominent among these standards are ISO 9000 & SEI-
CMM.
ISO 9000
ISO (the International Organization for Standardization)
is located in Switzerland and was established in 1947 to develop
common international standards in many areas. At present it has
127 members coming from the standard bodies in over 90 countries.
Its purpose is to facilitate international exchange of goods and
services by providing a single set of standards that people everywhere
would recognize and respect. ISO 9001, the standard in the 9000
series that pertains to software development and maintenance, identifies
the minimal requirements for a quality system.
SEI CMM
The Software Engineering Institute (SEI) is a federally funded
research and development center sponsored by the U.S. Department
of Defense through the Office of the Under Secretary of Defense
for Acquisition, Technology, and Logistics [OUSD (AT&L)]. Its
vision is "The right software, delivered defect free, on time
and on cost, every time"
In 1982 the U.S. Department of Defense formed a joint service task
force to review it's software problems. This resulted in the establishment
of the Software Engineering Institute (SEI) at Carnegie Mellon University
in December 1984. Beginning in 1986, the SEI and the Mitre Corporation,
led by Watts Humphery, began developing a process maturity framework.
That initial work then became the Capability Maturity Model V1.1
(CMM). The CMM consists of two documents, the model (tr24) and a
key practices document (tr25). The model describes the framework
of the CMM and outlines the Key Practice Area's. The key practices
document describes the Key Practice Areas in more detail.
ISO vs. CMM
There is a strong co-relation between ISO 9001 & CMM. It is
but logical, as both ISO & CMM have adopted each other's strengths
over the years. The biggest difference between the two documents
is the explicit emphasis of the CMM on continuous process improvement.
ISO 9001 addresses only the minimum criteria for an acceptable quality
system. Another difference is that the CMM focuses strictly on software,
while ISO 9001 has a much broader scope that encompasses hardware,
software, processed materials, and services. Talking only of software,
CMM is much more comprehensive & has the advantage of addressing
software specific issues.
At first glance, an organization with an ISO 9001 certificate would
have to be at level 3 or 4 in the CMM. In reality, some level 1
organizations have been certified. One reason for this discrepancy
is ISO 9001's high level of abstraction, which causes auditors to
interpret it in different ways. Another reason could be the greater
depth of a CMM-based investigation.
A software firm however does not thrive on the quality of the software
alone. When the management decides between CMM or ISO 9001, the
ideal choice would be to consider both, even with the significant
degree of overlap. Although either document can be used alone to
structure a process-improvement program, the choice for any one
of them would depend on the strengths & weaknesses of the software
firm. The markets addressed & customer perceptions play an important
part too.
In any case, organizations should focus on improvement to build
a competitive
advantage, not on achieving a score - whether that is a maturity
level or a certificate. The goal should always be Total Quality
Management & that involves not only becoming an ISO or CMM organization,
but imbibing the spirit of quality in the organization.
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