Power BI and Analysis Services rely on a semantic model based on the Tabular Object Model (TOM). Even though there are different tools to manipulate these models – we suggest using Tabular Editor – the underlying concepts are identical because the engine and the data model is the same: we call it the Tabular model. This article is based on a section of The Definitive Guide to DAX (second edition) and on the Different types of many-to-many relationships in Power BI video.