The book is dedicated to one of the important areas of theoretical and experimental physics and engineering - modeling of physical phenomena and processes. Over the past two decades, the considerable efforts are made to develop methods allowing the design of the mathematical models with the lowest discrepancy from the observed material object. Numerous methods and criteria have been proposed to achieve this goal. However, all of them are focused on identifying a posterior uncertainty caused by the ineradicable gap between model and a physical system. The present book is focused to formulate the a priori interaction between the level of detailed descriptions of the material object (the number of recorded variables) and the lowest achievable total experimental uncertainty of the main parameter. In this book there are collected the materials that are necessary for the optimal design of physical-mathematical models describing physical phenomenon or technological process. The author hopes that the book may be useful for scientists and engineers working in the enterprises and organizations of the corresponding profile and students of universities and colleges.