Responsibilities

• Select and switch DuckLake catalogs
• Refresh catalog metadata (dataset list, schema versions)
• Provide catalog context for query execution

Aggregate: Catalog

The Catalog aggregate enforces single active catalog invariant.

State Machine

NoCatalogSelected → CatalogActive(ref, metadata)

Key Value Objects

• CatalogRef: URI reference to DuckLake catalog (e.g., ducklake://hf/sciexp/fixtures)
• DatasetInfo: Dataset name, table count, schema version
• CatalogMetadata: Collection of datasets with refresh timestamp