I have been dealing with many Power BI challenges in my professional life as a Power BI consultant and a trainer. Challenges normally come as calculation or DAX questions, or sometimes as a performance question. However, after digging deeper into the problem, soon, it will be revealed that the problem is related to a more fundamental challenge; data modeling.If you have a Power BI implementation with many calculation-related or performance-related issues, I strongly suggest looking into your data model because that is where most of the problems start.A good data model is a great base, which upon that, you can build up many stories of calculations and analysis. A bad data model causes problems on every level that you add upon it, and might sometime cause the whole solution to collapse.Fortunately, data modeling is not rocket science. I explained the basic principles of the data modeling with examples in this book. Use this book as the learning path towards a better data model. Most of the tips mentioned in this book are product-agnostic (such as star-schema, dimension, and fact tables). However, this book is particularly designed and developed for a Power BI product user.This book is for you if you are building a Power BI solution. If your task is only visualizing the existing data, this book might not be needed for you. However, What I have seen in many cases, is that the requirement starts with just visualize the data, and then more data tables appear, and you get into the tunnel of data modeling without knowing the principles of it. This book is a guide for you through that tunnel.