This page supplements the analysis of BSDM in Chapter 4 by giving an example of the mechanism for determining which states are accessible in the detailed process model.
A final state, 
, is accessible from itself, without any process
applications or from the current state, X, if
there is an applicable process, P; and we make the changes for P
which are given in Ch to yield intermediate state 
; and we
remove all the deletions, De, stipulated by P and add all the
new information, Or, originated by P to give new state 
;
and 
is accessible from 
.
We need to define the processes which will be responsible for
moving between states. We shall do this using a standard format in
which we give the name of the process goal (always of the form
with P being instantiated to one of
the process names from the table in Figure 4.3). For
each we define the trigger which would allow us to apply the process;
the operations which the process performs when triggered; and the
changes to each of the components of the process scope (Or, Re,
Ch, De). Our three example processes appear in Figures 1,
2 and 3. Notice that the trigger, operation
and effects conditions for each process could be parcelled together in
a single expression defining the whole process:
Figure 1: Definition of grade award process
Figure 2: Definition of grade revision process
Figure 3: Definition of registration withdrawal process
To complete our basic model all we need is a definition of the conditions for assigning grades. These are given formally below.
We give an `a' grade if both exam score (
) and practical
score (
) are 75 or over. A `b' grade is given if both
marks are at least 65 but at least one is under 75. A `c'
grade is given if both marks are at least 50 but at least one is
under 65. A `d' grade is given if either mark is below 50.
