Many analysis techniques have been applied by the engineers to assess the system
dependability during the last four decades. Such techniques are used for the prediction,
verification, and improvement of dependability properties, mainly reliability,
availability, maintainability, and safety. They help in answering the questions that
are most pressing to an engineer, such as: Is the flight control system able to tolerate
N simultaneous equipment failures?When a shutdown occurs, howlong does it take
to recover the system? Is the system able to provide the service to the user during a
given time period? And so on.
A list of the primary techniques, recommended by the international standard
(IEC-60300-3-1 2003) for the dependability assessment, is shown in Table 6.1:
they are mainly used early in the software life cycle, that is during the requirement
and design activities. It is worth to mention that the list is a coarse classification
provided by the standard of the primary dependability techniques: for example, the
Petri Net analysis technique encompasses all the Petri Net semantics together with
the correspondent solution methods.
There is no a general rule for the selection of the best technique to be applied for
assessing the dependability of a specific system. Nevertheless, the IEC standard