Left-to-right flow vs top-to-bottom drill-down.
Two axes of lineage: horizontal traces data flow from sources to targets; vertical traces drill-down within a single asset, from column to table.
Where it lives: Article 2025-09-27.
[Read the article ↗](https://medium.com/@jacovanderlaan/beyond-sql-traceability-understanding-horizontal-vs-3e184af6d952)