OptionalChunkMJ: Content Item Chunks row id, when the indexed unit is a chunk rather than a whole item.
OptionalContentParent MJ: Content Items id.
OptionalEndEnd of the chunk's time window, in ms.
OptionalModalityChunk modality — text, image, audio, video, or multimodal.
OptionalPageOne-based page number for paginated sources.
OptionalStartStart of the chunk's time window, in ms, for audio/video.
Chunk-level provenance recovered from an external index document.
External indexes are populated outside MemberJunction, so these fields are present only when the indexing pipeline chose to emit them. Every field is optional by construction.