become the accepted route to competitive advantage
  (read quality). The rigorous standards of the Deming
  Prize represent to all manufacturing companies a de-
  manding guide for innovation towards quality.
  The quality of software products, in contrast to manu-
  facturing products, has the reputation of not being
  measurable, and thus hard to be  managed. TQM,
  however, should be applied in the software industry,
  since  manufacturing  equipment  and  maintaining
  software have common ground, as both pump as much
  throughput through their facilities as possible, face
  demand fluctuations and constantly change the struc-
  ture of their facilities.
  The software industry, like the manufacturing industry,
  should adopt the TQM approach by realising that
 variations in performance are inherent to every system
 and that clients are more concerned with variation of
 response time than average response time. Even
 though the Japanese software industry is far from
 matching the productivity levels of Japanese manufac-
 turing (if it were, we would all use Japanese spread
 sheets  and word processors),  TQM,  with proper
 adaptation and understanding, can be applied to
 improve the quality of software development and
 maintenance. "If Japan can ... -why can not we?"
 Performance variations are classified either as System-
 atic or Special. Systematic variations are inherent to
 the system. The elimination of Systematic variations
 requires a change to the system and is fully controlled
 by management. Errors that can be identified cause
 Special variations. The elimination of Special vari-
 ations require a change to the way a system is used
 and thus, may be driven by the clients. It is
 management's responsibility to classify variations as
 Special  or  Systematic  and act  accordingly.  Dr.
 Deming's empirical observations showed 96 per cent
 of the variations to be Systematic and 4 per cent Spe-
 cial. Part 5 of this paper shows how to classify vari-
 ations as Special or Systematic using Control Charts.
As performance variations are inherent to systems.
management must aim at stabilising systems. System
stability  is a  desirable  state  of random variation.
Performance variations in a stable system have the
following properties: their limits are predictable, they
comply to only one distribution pattern, they are
systematic (i.e. due to limitations inherent in the
system) and they may cause poor performance (e.g.
produce too many cases of unacceptable transaction
duration).
A  stable  system  delivers  consistent  (predictable)
performance that can be improved by analysis and
change. A system that is unstable produces inconsis-
tent performance. The resulting variation may be so

 wide that it would be hard to say whether a given
change has improved the system. We aim at having a
 stable system in order to  predict performance, with
regard to the clients' productivity, ISD's capacity
planning, measure the effects of changes in the system
and forecast the cost of improving clients' service.
Stability is not an end in itself. Once a system is
stable, work to improve  quality  and economy of
production must commence by never ending reduction
of variations and the navigation of attributes averages
in a desirable direction. Given this emphasis upon the
responsibility for the different types of variation. Dr.
Doming was able to contain his message in a single
sentence:
         "It is good management to reduce the vari-
         ation of any quality characteristic [say re-
         sponse time -AO], whether this characteristic
         be in a state of stability or not, and even
         when few or no defects are being produced".

   QUALITY MANAGEMENT IN THE MAINTE-
                 NANCE PHASE
Assuming you have the piece of software that delivers
the features required by your clients, how can you best
deal with statements most frequently heard, such as:
- "The system is slow "

         Figure 1
Statement frequently heard

- "The quarterly processing was not completed ^
time, though in the March quarter it was"

102