BUILDING A SEMANTIC LAYER: WHAT IT IS AND HOW WE DID IT AT POSTHOG

Summary from the TLDR Founders newsletter

A semantic layer is a dictionary of definitions that agents and humans read from. It doesn't copy data, replace a warehouse, or move a single row of data. It sits on top of the data that exists and describes it. The semantic layer gives everyone a single place to read definitions from so that the team is on the same page. This post tells the story of how PostHog built a semantic layer into its context warehouse.