Introduction

Closed equation format is the format of equations we are familiar with, for example,

To convert a closed equation to an open equation, the closed format equation is rearranged with all the terms on one side. The equation is then evaluated to find the residual. For example;

Why would we want to work with open equations?

• For linear equations, any term in the equation, (not just the left-hand term), can be found without the need rearrange the equation or solve it via iteration
• If the model is over-specified the use of open equations provides a method to reconcile the data
• Inter-related equations can be linked by simple connection equations, rather than by eliminating variables and equations