Conversely there is no reason (other than
aesthetic) why a user should choose ???Helvetica??? rather than ???Ariel.??? Each must be tested for and thus
each will form an explicit operational profile (with every variable). Conversely changing the Normal
style typeface requires an implicit operational profile (with sample variables).
The distinction between implicit and explicit operational profiles is important because implicit profiles
are usually much smaller and manageable.
Implicit profiles require far fewer variables: the sum of all examples from all sets of interest. Explicit
profiles by contrast require the product of all possible key input variables. This can get big (Table 7.6).
Create a key input variable matrix (Figure 7.14) to see which interact and how. Include the environmental
and configuration variables in this. In this matrix key inputs (in this case MS Word commands) are
shown in column and row. The figure should be read like this:
Ctrl+S (First) can be followed by Ctrl+O (Second)
because there is a ???1??? in cell D3. Thus it is normal to be able to open a document after having saved another.
Ctrl+V (First) cannot be followed by Ctrl+C (Second)
because there is an ?????“??? in cell H9 and because it is impossible to copy something without choosing it
first (ignore the possible use of the mouse in this example).
Note that in Word v.x we can close a document with the Find window open. It is then impossible to
open another document.
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