Fedora stores all of the repository content in OCFL objects.

This content consists of three types of files:

1. The user-content files (such as PDF, TIFF, TXT, MP4, etc.)
2. RDF files containing user-properties related to the OCFL object and/or user's content files
3. Fedora-specific JSON "header" files containing system-properties related to the OCFL object and/or user's content files

For each user-content and RDF user-properties file, Fedora needs to retain system metadata to have a full interpretation of the file. These "system metadata" files are call Fedora Header Files.

This document describes the format and elements contained within Fedora Header Files. The location and naming conventions for these header files is described in the Design - Fedora OCFL Object Structure wiki page.

General

All header files are serialized as JSON documents according to the following JSON Schema:

{
  "$schema": "http://json-schema.org/draft/2019-09/schema#",
  "$id": "https://fedora.info/schemas/2020/06/06/headers.json"

  "type": "object",
  "properties": {
    "id": {"type": "string", "format": "uri"},
    "parent": {"type": "string", "format": "uri"},
    "stateToken": {"type": "string"},
    "interactionModel": {"type": "string", "format": "uri",
      "enum": ["http://www.w3.org/ns/ldp#NonRDFSource",
               "http://www.w3.org/ns/ldp#RDFSource",
               "http://www.w3.org/ns/ldp#RDFSource",
               "http://www.w3.org/ns/ldp#Container",
               "http://www.w3.org/ns/ldp#BasicContainer",
               "http://www.w3.org/ns/ldp#DirectContainer",
               "http://www.w3.org/ns/ldp#IndirectContainer",
               "http://fedora.info/definitions/v4/repository#ArchivalGroup",
               "http://fedora.info/definitions/v4/repository#NonRdfSourceDescription",
               "http://fedora.info/definitions/v4/webac#Acl" ]
    },
    "createdDate": {"type": "date-time"} "2020-06-03T23:59:00.284677Z",
    "createdBy": {"type": "string"}
    "lastModifiedDate": {"type": "date-time"} "2020-06-03T23:59:00.284677Z",
    "lastModifiedBy": {"type": "string"} "2020-06-03T23:59:00.284677Z",
    "archivalGroup": {"type": "boolean"},
    "objectRoot": {"type": "boolean"},
    "deleted": {"type": "boolean"}
  },
  "required": ["parent", "id"],
  "additionalProperties": false

  $comment NonRDFSource resources have additional properties
  "if": {
    "properties": {"interactionModel": {"const": "http://www.w3.org/ns/ldp#NonRDFSource" }
  },
  "then": {
    "properties": {
      "mimeType": {"type": "string"},
      "filename": {"type": "string"},
      "contentSize": {"type": "integer"},
      "digests": {"type": "array",
         "items": {"type": "uri"} },
      "externalUrl": {"type": "uri"}
      "externalHandling": {"type": "enum"}
    },
    "required": ["mimeType", "filename", "contentSize", "digests"]
  }

}

Header files associated with user-content files

{
  "parent": "info:fedora",
  "id": "info:fedora/binary",
  "filename": "",
  "mimeType": "application/x-www-form-urlencoded",
  "interactionModel": "http://www.w3.org/ns/ldp#NonRDFSource",
  "lastModifiedDate": "2020-06-03T23:59:00.284677Z",
  "createdDate": "2020-06-03T23:59:00.284677Z",
  "stateToken": "5F789A9AAD061811FBB9BB0DE4B998C8",
  "contentSize": 9,
  "digests": [],
  "deleted": false,
  "archivalGroup": false,
  "objectRoot": true
}

Header files associated with RDF user-properties files

1. Containers

   1. {
        "parent": "info:fedora",
        "id": "info:fedora/container",
        "interactionModel": "http://www.w3.org/ns/ldp#BasicContainer",
        "lastModifiedDate": "2020-06-03T23:58:03.148409Z",
        "createdDate": "2020-06-03T23:58:03.148409Z",
        "stateToken": "DCEF22546A9D93D0203E96D1682DF9F8",
        "deleted": false,
        "archivalGroup": false,
        "objectRoot": true
      }

2. Binary descriptions

   1. {
        "parent": "info:fedora/binary",
        "id": "info:fedora/binary/fcr:metadata",
        "interactionModel": "http://fedora.info/definitions/v4/repository#NonRdfSourceDescription",
        "lastModifiedDate": "2020-06-03T23:59:00.280677Z",
        "createdDate": "2020-06-03T23:59:00.280677Z",
        "stateToken": "74A51841F559D31E3EBD40EFE2DE29E3",
        "deleted": false,
        "archivalGroup": false,
        "objectRoot": false
      }

3. ACLs

   1. {
        "parent": "info:fedora/new",
        "id": "info:fedora/new/fcr:acl",
        "lastModifiedDate": "2020-06-05T01:15:29.406689Z",
        "deleted": false,
        "interactionModel": "http://fedora.info/definitions/v4/webac#Acl",
        "createdBy": "fedoraAdmin",
        "createdDate": "2020-06-05T01:15:29.406689Z",
        "lastModifiedBy": "fedoraAdmin",
        "stateToken": "FF048B326D1DED62BDCB84D38DC7CB41",
        "archivalGroup": false,
        "objectRoot": false
      }