In thermodynamic consistency tests we have to face the problem of choosing an approximating function that causes negligible error with respect to the possible systematic error of the measured data. For the estimation of thermodynamic model parameters and for the evaluation of the function values we usually have to apply more than one software or programming language. These two facts mean a complex problem in several thermodynamic calculations: to find or to develop the suitable mathematical method and software, and to solve the problem of information flow between the different applications. In our paper we show an interesting solution for the mathematical,and information technological problem of ternary Vapour-Liquid calculations.