A simple example involving assignments elements and components is as
follows. Suppose that 
are element names, that 
is an
assignment including functional indices, and that 
and 
are the names of components summarising many like quantities. A number
of declarations are shown in Figure 6.1. These are as
follows:
(the latter given an
expectation of nine; the former having 
by default)
gathered into the base G, followed by their variance-covariance
matrix.
and ; covariances between and 
, and covariances
between and 
. All other variance-covariance
specifications (for example, between V and W) are to be zero by
default. . , together with
the definition of the element 
as a termination criterion for
the recursive assignment.
is not an element, and so a check is
made to see whether it is an assignment. It is, so D.1 is replaced by
the linear combination it represents, and the linear combination to be
built is thus 
. Expectations, variances
and covariances are now constructed for 
and between and
from the explicit and implicit belief specifications given.
Now consider Figure 6.2. This is exactly the same
sequence of commands as in Figure 6.1, except for the
insertion of an extra command line building explicitly as the
penultimate command line. This illustrates the second form of the syntax
in that the assignment is taken, and the element
constructed. It also illustrates the
forgetfulness property addressed above in that the element
constructed therafter will have different beliefs to the
constructed in Figure 6.1, as the component constituents
of the assignment will have been forgotten in the second case.
Figure 6.1: Constructing new quantities
Figure 6.2: Illustrating forgetfulness