Property presence and ordering

ODCS schema objects support two independent Packata boolean custom properties:

schema:
  - name: orders
    customProperties:
      - vendor: packata
        property: allowAdditionalProperties
        value: false
      - vendor: packata
        property: enforcePropertyOrder
        value: true
    properties:
      - name: id
        logicalType: integer
        required: true
      - name: description
        logicalType: string
        required: false

Omission independently defaults to allowAdditionalProperties: false and enforcePropertyOrder: true. A property’s native required flag determines presence; ODCS omitted/false means optional. Nullability is independent: a required column may allow null values, and an optional column may forbid null values when present.

Additional properties are actual columns not declared in the contract. Enforced order compares only present declared properties, ignoring permitted extras. For declared [id (required), name (optional), email (optional)], defaults accept [id] and [id,email], but reject [email,id], [id,country], and [name]. With both booleans true, [id,country,email] passes and [email,country,id] fails. With extras allowed and order disabled, [email,country,id] passes. No overlap requirement is implied if every declared property is optional.

These extensions require actual boolean values. Strings such as "false", duplicates, and declarations on owners other than schema objects are errors. The obsolete Packata propertyMatching/propertyOrder extensions produce migration diagnostics. Other vendors remain untouched. Original declarations remain in metadata.

The canonical API replaces the former DataSchema.FieldMatching and the in-flight PropertyMatching/PropertyOrder enums with AllowAdditionalProperties and EnforcePropertyOrder booleans. DataField.Required retains presence and DataField.Nullable retains nullability. Direct canonical construction defaults to true/false (extras permitted, unordered); mappers explicitly apply format defaults.

To migrate old ByName or Subset/Any, use true/false and make all declared fields required if their presence was guaranteed. OrderedExact or Equal/Declared becomes false/true with every field required; Exact or Equal/Any becomes false/false with every field required. ClosedOptional or Superset/Any becomes false/false with optional fields. The former Partial/Any requires true/false, optional fields, and a preserved native overlap restriction; the booleans alone are not equivalent.

DPv2 fieldsMatch	AllowAdditionalProperties	EnforcePropertyOrder	Field Required
exact (default)	false	true	Every field
equal	false	false	Every field
subset	true	false	Every field
superset	false	false	Optional unless a native key requires presence
partial	true	false	Optional unless a native key requires presence

Native DPv2 partial additionally requires at least one matching field. The mapper retains datapackage.fieldsMatch metadata and structural validation enforces that restriction; satisfaction retains Unknown for this additional native condition. Native constraints.required still controls missing/null cell values independently. DPv2 positional/name-based mapping modes are retained. No reverse DPv2 export is introduced; mixed optionality or enforced order with extras may have no exact native equivalent.

Contract inspection exposes the booleans and per-field requiredness. Diff reports changes to either setting and declared sequence; compatibility conservatively reports unresolved containment as Unknown. Satisfaction considers required presence, additional-property guarantees, and relative order independently. Unsupported semantics remain Unknown. Category-value ordering (ValueDomain.Ordered) is unrelated.

Runtime column-presence, extras, and ordering checks belong to structural validation (#526); null and other cell-value checks belong to #597. Preview and inference do not enforce these validation requirements or infer future guarantees from a sample.

JSON Schema record export retains additional-property permission, field requiredness, and native partial overlap. Column order applies to tabular inputs rather than JSON object member order, and remains outside that record representation.