GPS-X Technical Reference

GPS-X Composite Variable Calculations 40
Box-and-arrow Diagrams
The nomenclature used in the box-and-arrows diagrams is explained in Figure 4-1.
Figure 4-1 – Diagram Nomenclature
The variables in the boxes and above the connection lines are known (either previously
calculated or user input). The variables in BOLD CAPITALS represent the composite
variables which are to be calculated. The connection line shows the direction of
calculation and always begins from a known or boxed variable. Multiple lines converging
to one unknown variable imply a summation operator. In the example shown above, the
variable Y1 is calculated by multiplying the variable x1 by the stoichiometry parameter k
and summing it with variable x2. If no stoichiometry parameter appears above the
connection line, it implies a default value of 1. When a broken line circle is drawn on the
lines, it indicates that the stoichiometry parameters for these lines are model dependent.
In certain situations two or more calculated composite variables are used to calculate an
additional composite variable. For example, Y3 is calculated by adding the calculated
composite variables of Y1 and Y2.
In addition to diagrams which explain the general way composite variables are
calculated, composite variable tables are used to explain model-specific calculations. The
nomenclature used in the composite variables tables is explained in Table 4-1:
Table 4-1 – Example Composite Variable Calculations
SCOMP XCOMP TCOMP
sa 1 1
sb ksb ksb
xa 1 1
xb kxb kxb
GPS-X Technical Reference