0008: Reject the historical Action input quality

Esdieff rejects sdfRequiredInputData at assessed SDF vocabulary positions with an explicit, helpful error. The pre-standard Action-input mechanism was removed from the specification, and its legacy grammar production was subsequently removed. Supporting its historical semantics would introduce compatibility behavior outside the current Action model.

The diagnostic identifies the unsupported historical quality and points to sdfInputData. Where input has multiple named fields, it explains the current type: "object", properties, and required structure described in RFC 9880, Section 5.3. Migration requires reviewing the input description rather than renaming a keyword.

The final RFC still lists the name in its registry, and its framework syntax has liberal extension points. Consequently, this is an explicit acceptance restriction, recorded in the agreed restrictions list, rather than a claim that every occurrence is a mandatory RFC violation. Esdieff’s selective restriction does not imply use of the entire closed validation syntax from Appendix A.

The restriction applies to assessed vocabulary positions, including document and information-block qualities, and to effective definitions after JSON Merge Patch. Catalogue checking still assesses supplied definitions independently. Given Names, sample-data entries, and arbitrary keys within opaque extension content are not vocabulary positions. Raw inspection and independent checks remain available when this error occurs.

Considered Options

Preserving this historical quality as ordinary optional content would conceal a removed mechanism behind extension handling. Automatic conversion would require assuming the old model’s intended input structure. Explicit rejection provides an actionable path to the current Action model.