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Wire Format

The MetaObjects wire format is JSON. Metadata files live in metaobjects/ at project root, organized by domain concept (e.g., meta.commerce.json). Each file declares its package on the root node.

Canonical fused-key form

Every node is a one-key map: { "<type>.<subType>": <body> }. The wrapper key fuses type and subType — there is no separate subType body key.

{
  "metadata.root": {
    "package": "myapp::commerce",
    "children": [
      {
        "object.entity": {
          "name": "Program",
          "children": [
            { "field.long": { "name": "id" } },
            { "field.string": { "name": "title" } },
            { "identity.primary": { "@fields": ["id"] } }
          ]
        }
      }
    ]
  }
}

Body key order

Within a node body, keys appear in this exact order in the canonical form:

  1. name — when non-empty
  2. package — when set
  3. extends — when set
  4. abstract — when true
  5. overlay — when true
  6. isArray — when true (structural, NOT an @-attr)
  7. @-prefixed attributes — alphabetical order within this section (e.g. @column, @currency, @default, @fields, @locale, @objectRef)
  8. children — when non-empty (declaration order, NOT alphabetized)

The reserved structural keys are exactly those listed above. In canonical JSON, everything else is an @-prefixed attribute; @-prefixing a reserved word (e.g. @isArray) is invalid (ERR_RESERVED_ATTR). YAML authoring is sigil-free (ADR-0006): the same closed reserved set is bare, every other key is a bare attribute, and the desugar re-adds the @ when lowering to this canonical form. Array-ness is the bare reserved isArray (YAML: the [] key-suffix sugar).

Package + file organization

Multiple objects per file when they share a domain. Projections live inline with their base entities. Files are scanned recursively under metaobjects/. Same-package + same-name objects across files are merged by the Loader via overlay semantics.

{
  "metadata.root": {
    "package": "myapp::commerce",
    "children": [
      { "object.entity": { "name": "Program", "children": [/* ... */] } },
      { "object.entity": { "name": "Purchase", "children": [/* ... */] } },
      { "object.entity": { "name": "ProgramSummary", "extends": "Program",
          "children": [/* ... */] } }
    ]
  }
}

Attribute values

  • @fields accepts a string in authoring ("@fields": "id") but is normalized to an array in canonical ("@fields": ["id"]).
  • Boolean attrs: "@filterable": true, "@default": false.
  • Numeric attrs: "@pageSize": 25, "@default": 0.

See metamodel.md for the type vocabulary and conformance-tests.md for the canonical serializer contract.