pub.layers.expression

An Expression is any linguistic unit in Layers — from a single morpheme to a full document. Expressions are recursive: a word is part of a phrase, which is part of a sentence, which is part of a paragraph, which is part of a document. Top-level expressions (documents, recordings) have no parent; all other expressions reference their containing expression via parentRef. Segmentation records define how a parent expression is broken into child expressions.

Types

main

Type: Record

An expression record representing any linguistic unit — from a full document to a single morpheme — with optional recursive nesting.

Field	Type	Description
id	string	A corpus-level unique identifier (headline, URL, document ID, etc.).
kindUri	at-uri	AT-URI of the expression kind definition node. Community-expandable via knowledge graph.
kind	string	Expression kind slug (fallback when kindUri unavailable). Known values: document, transcript, dialogue, social-media, email, article, recording, video, multimodal, code, section, paragraph, chapter, turn, utterance, heading, list, sentence, clause, phrase, word, morpheme, character, other
text	string	The full raw text of the expression. All character-offset spans reference this string.
mediaRef	at-uri	Reference to an associated media record (audio, video, image).
mediaBlob	blob	Optional inline media blob.
language	string	BCP-47 language tag for the primary language.
metadata	ref	Ref: pub.layers.defs#annotationMetadata
features	ref	Arbitrary document-level features and metadata. Ref: pub.layers.defs#featureMap
sourceUrl	uri	URL of the external web resource this expression was derived from or annotates.
sourceRef	at-uri	AT-URI of an external ATProto record this expression is derived from or annotates (e.g., a standard.site Leaflet post, a com.whtwnd blog entry, an app.bsky.feed.post, an at.margin.bookmark).
eprintRef	at-uri	Reference to an eprint record that this expression is associated with.
knowledgeRefs	array	References to knowledge base entries relevant to this expression. Array of ref: pub.layers.defs#knowledgeRef
parentRef	at-uri	Reference to the parent expression this one is nested within. Absent for top-level expressions (documents, recordings, etc.).
anchor	ref	How this expression attaches to its parent (character span, temporal span, etc.). Ref: pub.layers.defs#anchor
languages	array	Additional BCP-47 language tags for multilingual or code-switching expressions. Array of strings
createdAt	datetime	Record creation timestamp.