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Experimental The Ossie integration is under active development and will be released soon, with the format interchange features it enables close behind. What Experimental means.
Apache Ossie (Incubating) — formerly the Open Semantic Interchange (OSI) — is an open, vendor-neutral specification for exchanging semantic models between tools. It defines a machine-readable format for describing datasets, relationships, fields, and metrics, along with the business context around them, so that any tool in a data stack can produce or consume semantic definitions without losing meaning. The project is incubating at the Apache Software Foundation, developed in the open on GitHub, and backed by a coalition of data and analytics vendors. Its goal is to make a business concept like “Monthly Active Users” resolvable consistently across warehouses, BI tools, and AI agents, regardless of where it was originally defined.

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What Ossie covers

Ossie standardizes the shape of a semantic layer as an interchange format:
  • Semantic models — the top-level unit exchanged between tools.
  • Datasets — the queryable tables in a model.
  • Relationships — how datasets connect to each other.
  • Fields — the dimensions on each dataset.
  • Metrics — the measures defined against fields.
  • AI context — the descriptions and business meaning consumers (including AI agents) rely on.
  • Custom extensions — a custom_extensions slot for tool-specific detail that would otherwise be lost in a round-trip.

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How Ossie maps to the Lightdash semantic layer

The Lightdash semantic layer already models the same building blocks Ossie standardizes: Lightdash will use Ossie as an interchange format for the semantic layer: you’ll be able to import Ossie models into a Lightdash project, export a Lightdash project as Ossie, and round-trip through custom_extensions for detail the base spec does not yet cover.

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Where to learn more