What is a semantic model in Power BI?

A semantic model, previously called a dataset, is the data foundation on which a report is built. It contains the tables, the relationships between them, and the measures that are calculated.

The report is just the view

Multiple reports can be based on the same model. This means that when someone corrects a calculation in the model, it is corrected in all the reports at the same time. Conversely, if the calculation is in the report, it must be corrected separately in each report, and sooner or later the reports will show different figures.

One model beats many

The most common reason why two departments report different revenue figures is that they each have their own model with its own definition of revenue. Agreeing on a single shared model is more of an organizational task than a technical one, and it is almost always worth the effort.

Who should own it

The model should have a clearly designated owner who approves changes. Without one, it accumulates fields and metrics whose purpose no one remembers, and eventually no one dares to remove anything.