DATA_FORMAT.md

Data format

The real and synthetic directories each have train and test splits. Each JSON file contains one chart and its annotations. Real records contain references; synthetic records refer to a same-stem PNG in the same archive.

Shared fields

Field	Meaning
sample_id	Unique frozen sample identity
benchmark_id	Secondary test identity; empty string for training records
source_type	real or synthetic
track	real, layout, or nb2; the latter two are generation tracks
source_channel	Retained source collection or generation channel
width, height	Annotation-input image dimensions in pixels
image_sha256	SHA-256 of the exact annotation-input image file bytes
scene_graph	Parsed scene graph JSON object
scene_graph_sha256	SHA-256 of the compact UTF-8 JSON serialization with ensure_ascii=False and one trailing LF
spatial_relations	JSON array containing stored spatial relationships
spatial_policy	Identifier of the spatial relationship selection policy
annotation_version	training-0.6 or heldout-v2-target-0.6
human_gold	True for the 1,000 manually verified test charts; false for the training split

Scene graphs

The JSON schema describes the graph structure. The top-level fields are high_level_description, style_description, and compositional_deconstruction; the latter has background and nodes fields.

Each node has label, node_kind, parent, bbox, and descriptive attributes. node_kind is element or group. Elements carry element_type, role, and role_family; groups carry group_type. Text elements also carry their recognized text. Node IDs are labels such as <text 1> or <chart 4>. parent points to another node label or the implicit ROOT.

Bounding boxes are [y0, x0, y1, x1] in normalized integer coordinates from 0 to 1000. To convert to image pixels, multiply x coordinates by width / 1000 and y coordinates by height / 1000. There is one hierarchical relationship for each explicit node, including links to ROOT.

Spatial relationships

Every relationship has relation_type, from_id, and to_id. Endpoints reference graph node labels.

relation_type	Additional fields
relative_position	directions: applicable left, right, above, or below relations from the first node to the second
aligned_with	basis: aligned edges or centers (left, right, top, bottom, center_x, center_y)
bbox_overlaps	No additional fields; boxes overlap with positive area
bbox_distance	Boolean is_near, plus diagnostic distance_px and distance_ratio (normalized by the image diagonal)

The policy nominates nearby siblings, prioritizes group structure, and stores complete bundles of applicable relationship types for selected pairs. Hierarchy is preserved separately through parent. Missing spatial relationships are unrecorded pairs, not negative examples.

Real-image references

No real-image binary column is included. At least one source-page, image, or public archive reference is present for every real record.

Field	Meaning
source_url, source_urls	Retained source webpage URL and complete URL list; a webpage is not necessarily an image download
image_url	Available direct image URL, or null
image_url_candidates	Candidate assets associated with source metadata; these may refer to different images on the same page
image_url_provenance	How image_url was obtained or matched; null when no direct URL is assigned
url_status	Reference category: source_page_reference, image_url_from_source_metadata, image_url_hash_matched, or public_archive_member_reference
source_image_sha256	SHA-256 of the original source file when retained; may differ from the prepared input hash
source_frame_index	Zero-based frame selected from an animated or multi-frame source, or null
image_archive_url	Pinned URL of an existing public upstream TAR archive, or null
image_archive_member	Exact member name in that archive
image_archive_offset, image_archive_length	Member data offset and length, in bytes
image_archive_sha256	SHA-256 of the complete upstream archive
input_conversion	Recorded conversion from source image to annotation input when known; null means unspecified

Archive references point to existing upstream archives; no real images are uploaded here. To obtain a member from an uncompressed archive, use the inclusive HTTP byte range offset to offset + length - 1, provided the server supports ranged reads. Alternatively, download the archive and extract the exact member. Verify the source file against source_image_sha256.

The annotation input may be an RGB PNG prepared from a JPEG, transparent image, EXIF-oriented image, or selected animation frame. Preserve frame selection and conversion before comparing with image_sha256. The supplied dimensions describe that prepared input. Do not assume that the current main image on a source webpage is the annotated asset.

image_url_hash_matched records an existing content match during preparation, not a guarantee of continued availability. Live URL checking is not required for release. Candidate assets and source-metadata URLs are retained without a promise of reachability or an exact content match.

Synthetic images

image_file gives the same-stem PNG filename inside the archive. image_sha256 hashes these released file bytes. Author-bearing PNG text/EXIF metadata is removed while retaining pixel data. Dimensions remain those used by the annotations.

Boolean proximity

Let d be the minimum Euclidean gap between two axis-aligned boxes in image pixels, and let A be the smaller box area. is_near is true exactly when the boxes have no positive-area intersection, d <= 0.06 * min(width, height), and d <= sqrt(A). Edge or corner contact is near. Containment and positive-area overlap are not near. The thresholds use pixel geometry after converting normalized boxes. Stored distance fields are diagnostic; evaluation uses the Boolean flag.

Checksums

Hash scene_graph after serializing it with Python json.dumps(graph, ensure_ascii=False, separators=(",", ":")) + "\n", encoded as UTF-8. annotation_sha256 in the index hashes the exact JSON member bytes. image_sha256 hashes the PNG bytes for synthetic records and the historical annotation input bytes for real references. manifest.json lists all data shards and their SHA-256; SHA256SUMS covers public files except itself.