DCAT US 3.0

DCAT-US 3.0 is Data.gov's incoming metadata standard, replacing DCAT-US 1.1 (the 2014 Project Open Data schema). It is a JSON Schema 2020-12 implementation of the W3C DCAT v3 vocabulary, maintained at GSA/dcat-us.

Why it exists

• Overcomes v1.1's spatial/geospatial limits without needing a separate federal geospatial standard
• Adds first-class support for data services (APIs) and dataset series (recurring publications)
• Adds controlled-vocabulary support (Concept/ConceptScheme) instead of bare strings for theme/category
• Closely related to v1.1 -- new elements added, no major rework of existing ones

Status

• harvest.data.gov supports dcatus3.0 as a harvest source schema_type; sources go straight to VALIDATE, same as 1.1 (no TRANSFORM step needed)
• Harvester API's 3.0 catalog validator is documented as planned but not live yet -- 1.1 only today, see Harvester APIs
• Prerequisite for two other initiatives: inventory-app's move away from CKAN, and the Solr → Postgres search migration for catalog

Key structural differences from 1.1

• Root Catalog gets a service[] array (DataService) alongside dataset[], plus optional record[] (CatalogRecord) and nested catalog[]/hasPart[]
• contactPoint goes from a single vCard to a Kind object or a list of them
• theme/category go from bare strings to Concept objects, optionally scoped to a ConceptScheme
• spatial goes from a free string to a Location object (geometry/bbox/centroid/prefLabel)
• New top-level classes: DatasetSeries (recurring publications), DataService (APIs), CatalogRecord (catalog registration metadata), Concept/ConceptScheme (controlled vocabularies)

For the full field-by-field diff against 1.1, see DCAT-US 1.1 vs 3.0.

Notable spec design points

• CatalogRecord's @id has no declared requirement level -- a spec-valid record can have no identifier of its own, since it is primaryTopic and modified that carry the meaning.
• spatial (Location) can represent geography four different ways -- geometry, bbox, centroid, or prefLabel -- and a given record may populate any subset of them.
• Series membership can be dual: a dataset may legitimately appear both as a top-level catalog.dataset entry and as a DatasetSeries.seriesMember.

Source & schema reference

• Spec + JSON Schema: GSA/dcat-us
• Generated field docs: jsonschema/docs
• Local schema checkout: datagov-harvester/_external/dcat-us/ (git submodule)
• v1.1 schemas for comparison: datagov-harvester/schemas/dcatus1.1/
• Fixtures for both versions: datagov-harvester/example_data/dcatus/