DERIVATION_CONTRACT.md

Derivation Contract v1

1. Purpose

This contract defines reproducible access derivatives for the maxwellinked/time-lapse-artifacts archive. It does not define a research task, benchmark, aesthetic ontology, or theory of the recorded practice.

2. Source authority

Every derivative must record:

• source repository ID
• pinned source revision
• source record_id
• source repository path
• published source Xet file ID
• Hub-reported LFS SHA-256
• independently computed SHA-256 of the downloaded bytes
• source byte size
• source encoded duration
• source audio-stream presence

A derivative is invalid if its source identity cannot be resolved, the pinned revision or Xet file ID differs from the published metadata, or the downloaded SHA-256 differs from the Hub-reported LFS SHA-256. Xet identity and byte SHA-256 are distinct fields and must not be compared as if they were the same hash function.

3. Epistemic separation

3.1 Curator facts

Facts established through the source metadata, physical-work review, or documented provenance evidence.

3.2 Unresolved states

Null and unknown are valid states. They must not be converted into false, zero, absent, complete, or standalone.

3.3 Deterministic measurements

File hashes, encoded positions, image hashes, Hamming distances, dimensions, and stream properties may be computed without becoming interpretations of skill, intent, quality, completion, or real-time behavior.

3.4 Interpretations

Human and machine interpretations are outside the initial pilot. If added later, they must occupy a separately versioned namespace and may not overwrite facts or unresolved states.

4. Identity model

• record_id: persistent identity of one published video object
• work_id: persistent identity of one curator-verified physical drawing
• derivation_id: identity of one source object processed under one pinned generator contract

work_id remains null unless verified. Filename components such as Rec01, a shared date, or visual similarity alone do not establish work identity or sequence.

5. Completeness model

The following dimensions are independent.

5.1 source_master_status

• archival_master: curator has verified the object as an archival master
• active_derivative: curator has verified that the object is a shortened or otherwise active derivative
• unknown: master/derivative status is not established

5.2 visible_start_state

• blank_or_unmarked
• preliminary_work_present
• mid_process
• unknown

5.3 visible_end_state

• completed_signed
• completed_unsigned
• active_work
• unknown

These values describe what is documented at the visible endpoint. They do not judge aesthetic success or prove completion of the real process.

5.4 capture_extent

• full_available_process: curator has verified that the available recording spans the expected visible process range; this does not mean calibrated real session completeness
• starts_mid_process
• ends_mid_process
• starts_and_ends_mid_process
• unknown

No automated visual inference may populate these fields in the initial pilot.

6. Proxy transform

• video stream only; all audio removed
• fit within 1280 × 1280 pixels
• preserve stored orientation and aspect ratio
• force even output dimensions
• 30 encoded frames per second
• H.264 using libx264, preset=medium, crf=28
• request pixel format yuv420p; record the probed result separately
• accept FFprobe's yuvj420p alias when H.264 preserves full-range 8-bit 4:2:0 values; do not silently force full-range source values into limited range
• remove source metadata
• enable fast-start layout
• record the complete FFmpeg version string

Bit identity is guaranteed only for the recorded generator and FFmpeg versions. Output SHA-256 remains the authoritative derivative identity.

7. Progress-frame transform

• 21 positions: 0.00, 0.05, ..., 1.00
• positions refer to normalized encoded duration, never real drawing time
• the final position seeks to the last decodable frame interval before the reported encoded duration
• fit each frame within 1280 × 1280 pixels while preserving aspect ratio
• JPEG quality setting q:v=2
• remove source metadata
• record normalized position, requested seek time, exact SHA-256, 64-bit difference hash, and Hamming distance from the preceding sample

Repeated or near-repeated frames are reported. The pipeline does not label them meaningless, static, erroneous, or significant.

8. Audio rule

source_has_audio reports stream presence. audio_removed=true reports the proxy transformation. Neither field classifies audio content.

9. Validation-set rule

The set is selected to expose engineering failures, not to represent the archive statistically or aesthetically. Selection is deterministic and records one or more reasons per row. Wave assignment controls cost; it does not imply importance.

10. Publication boundary

Masters remain in the source archive. Derivatives live in this separate repository. A derivative may be regenerated or superseded without changing the source record. No unresolved source fact may be silently corrected here.