P&R proposes an initial value for all parameters. This initial value serves as a default value that can be modified to resolve constraint violations. The propose inference computes the value of the SELECTED PARAMETER. Figure 3 shows the inference with its knowledge roles: SELECTED PARAMETER, PARAMETER PROCEDURES and PARAMETER VALUES.
The SELECTED PARAMETER and PARAMETER VALUES are knowledge roles which were described in the previous section. The PARAMETER PROCEDURES computes the initial value of parameters. All parameters have a unique procedure, except the input parameters. In the VT application, for example, the procedure to compute the value of the sling-underbeam is equal to the car cab height plus the sling underbeam space.
Figure 6: The formalization of the
propose inference and its knowledge roles.
Figure 6 presents the formalization of
the propose inference and its knowledge roles. In (8),
the class of procedures is defined. The definition (9) associates a
unique procedure to each parameter, with the restriction
that input parameters do not have associated procedures. In (10),
the propose inference computes the value of the
SELECTED PARAMETER.