The model equations are at best an approximation to the real process.

• Adage: “All models are wrong, but some are useful.”
• Modeling inherently involves a compromise between model accuracy and complexity on one hand, and the cost and effort required to develop the model, on the other hand.
• Process modeling is both an art and a science. Creativity is required to make simplifying assumptions that result in an appropriate model.
• Dynamic models of chemical processes consist of ordinary differential equations (ODE) and/or partial differential equations (PDE), plus related algebraic equations.