fiftyone.core.annotation.hydrate_label_schemas

Annotation label schema hydration

Resolves applied_ontology references in label schemas by merging the referenced annotation ontology’s attributes into the schema’s attributes list, tagging merged attributes with a _source marker.

Copyright 2017-2026, Voxel51, Inc.

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Functions:

attributes_with_source(ontology)	Returns ontology attributes as dicts tagged with a _source marker.
hydrate_applied_ontology(label_schema)	Merges a referenced annotation ontology's attributes into a label schema.
dehydrate_applied_ontology(label_schema)	Strips hydration artifacts from a label schema before it is saved.
inline_applied_ontology(label_schema, ontology)	Permanently inlines an annotation ontology's attributes into a label schema as local copies and removes the applied_ontology reference.

fiftyone.core.annotation.hydrate_label_schemas.attributes_with_source(ontology: Any) → list[dict[str, Any]]

Returns ontology attributes as dicts tagged with a _source marker.

Parameters:

ontology – an ontology object whose .attributes are attribute specs with a .to_dict() method and whose .name identifies the ontology

Returns:

a list of attribute dicts, each carrying _source: ontology.name

fiftyone.core.annotation.hydrate_label_schemas.hydrate_applied_ontology(label_schema: dict) → dict

Merges a referenced annotation ontology’s attributes into a label schema.

If label_schema has an applied_ontology key that resolves to an annotation ontology, returns a new dict with the ontology’s attributes merged into the attributes list. Each merged attribute carries a _source: <ontology_name> marker. Attributes are matched by name and ontology values win on collision.

If the schema has no applied_ontology reference, the schema is returned unchanged. If the reference is dangling (deleted ontology) or points at a non-annotation ontology, the applied_ontology key is stripped from the returned schema and a WARNING is logged. This lets a subsequent save silently persist a clean schema rather than failing validation on the dangling reference.

Parameters:

label_schema – a label schema dict

Returns:

a hydrated copy of label_schema, a copy with applied_ontology stripped if the reference is dangling, or the schema unchanged when there is nothing to do

fiftyone.core.annotation.hydrate_label_schemas.dehydrate_applied_ontology(label_schema: dict) → dict

Strips hydration artifacts from a label schema before it is saved.

Companion to hydrate_applied_ontology(). When the schema has an applied_ontology that resolves to an annotation ontology, drops any attribute whose name matches an ontology-owned attribute and strips the _source marker from the remaining attributes.

Otherwise (no reference, dangling reference, or non-annotation reference) the schema is returned unchanged — the validator will surface the reference-level problem.

Parameters:

label_schema – a label schema dict, possibly carrying hydration artifacts from hydrate_applied_ontology()

Returns:

a deep-copied schema with hydration artifacts removed, or label_schema unchanged when there is nothing to dehydrate

fiftyone.core.annotation.hydrate_label_schemas.inline_applied_ontology(label_schema: dict, ontology: Any) → dict

Permanently inlines an annotation ontology’s attributes into a label schema as local copies and removes the applied_ontology reference.

Used when the referenced ontology is about to be deleted (or for any other “freeze the current ontology state into the schema” operation). Unlike hydrate_applied_ontology(), the merged attributes are NOT marked with _source — they are now first-class local attributes — and the applied_ontology key is stripped from the result.

The caller is responsible for resolving the ontology; this function does not load anything.

Parameters:

• label_schema – a label schema dict

• ontology – an AnnotationOntology whose attributes should be inlined

Returns:

a deep-copied schema with the ontology’s attributes merged in as locals and the applied_ontology reference removed