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Open table formats

System9 publishes and shares data in open formats so a consumer is not locked into a System9 client. Two distinct surfaces live here, and a datasheet will want to merge them, which it must not, because they have very different status.

Direction: both (served and, for Delta Sharing, consumed). Status: Partial. The available surfaces are named below.

Delta Sharing​

Delta Sharing is the recipient-facing protocol: a party outside the organization consumes a governed share with a profile file, using any Delta Sharing client, without being granted an account. It is implemented as a full, spec-shaped server (shares, schemas, tables, versioned metadata, and token-scoped file access), with a policy guard in front, a share is a governed grant, not a raw file handout. System9 also ships the client half, so it can consume another party's Delta share as a federated source.

Iceberg​

Two Iceberg-shaped surfaces exist, and they get different sentences:

  • Iceberg table management over managed tables, partial (live slice). The reachable slice is metadata publishing, materialization, schema evolution, liquid clustering, and sharing. The layer that makes a lakehouse format fast, file pruning, row-group statistics, z-order, projection indexes, partition evolution, are on the roadmap.
  • Iceberg REST catalog, catalog reads only. The served catalog answers config, namespaces, and tables with registry-backed metadata, and every read is policy-enforced (a forbidden table returns not-found rather than revealing its existence). But the write paths are in-memory only, and the load response does not carry a complete table descriptor, so this is not a working bring-your-own-engine surface. Treat it as a catalog-read integration; for a governed table read into a tool, use the PostgreSQL wire protocol.
Do not conflate the three Iceberg claims

"We support Iceberg" hides three different claims: a served REST catalog (catalog-reads only), Iceberg metadata publishing over managed tables (partial, live slice), and reading someone else's Iceberg as a federated source (outbound). State which one you mean.

  • Open sharing. Delta Sharing and the Iceberg REST catalog in depth.
  • Lakehouse tables, the managed table formats these surfaces publish.
  • Data Exchange, signed, offline-verifiable data sharing as an alternative.