The operational mode levels will usually
dominate. Thus training mode is less risky than the operational.
7.7.4 Define the System-Mode Profile
Systems operate in various modes: start-up, ???normal??? use, shut-down, training. A system-mode profile is
the set of system modes and their associated occurrence probabilities. In each mode a system will allow users
to use some set of functions. Many of these will be common to more than one mode. Each system mode
will therefore have an operational (and possibly a functional) profile. Systems may change mode according
to environment such as traffic levels. The basis on which systems can change mode needs to be established.
System modes aren??™t necessarily disjoint: thus one user may be in training mode, while another uses
the system, and a third acts as an administrator performing non-exclusive operations. For each user
group you then define the system-mode profile (see Table 7.5).
7.7.5 Determine the Functional Profile
Each mode will consist of a number of features or functions to which some user group will have access.
Hopefully, these are defined in the requirements specification but could (at a pinch) be redefined (as
shown in section 8.2) from a manual. These can be related to a process model of the system such that
the functions being accessed can be shown along with their probability (Figure 7.13).
TABLE 7.5 Sample system-mode profile
System mode Occurrence probability
Business use 0.
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