Many ask themselves, "Why would I use a semantic layer? What is it anyway?" In this hands-on guide, we’ll build the simplest possible semantic layer using just a YAML file and a Python script—not as the goal itself, but as a way to understand the value of semantic layers. We’ll then query 20 million NYC taxi records with consistent business metrics executed using DuckDB and Ibis. By the end, you’ll know exactly when a semantic layer solves real problems and when it’s overkill. It's a topic that ...