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metadata-patch.md

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Modifying metadata via Patch

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Contents:

Introduction

A user with write permission on a DSpace object may change any of its metadata using an HTTP PATCH request. All DSpace object types (Bitstreams, Items, Collections, etc.) support metadata changes in roughly the same way.

This guide is focused on metadata-only changes and omits non-metadata parts of the object's json representation for brevity. However, you should be aware that PATCH requests operate against the whole object, and may therefore modify other mutable attributes in the same request.

For additional information about PATCH support in DSpace, including request format and response status code details, see General rules for the Patch operation

The examples in each section below build on each other, assuming an initial metadata state of:

{
  "metadata": {
    "dc.title": [
      { "value": "Initial Title", "language": null, "authority": null, "confidence": -1 }
    ]
  }
}

Note: The metadata of items in submission is modeled in the same way described here -- as a map of metadata keys to an ordered array of values. The primary difference is where the metadata is located within the JSON representation. The documentation and examples below apply to archived items and other DSpace object types, whereas the WorkspaceItem Metadata document describes how item metadata can be modified during submission.

Adding metadata

With the add operation, you can add any number of metadata values in a single request.

You also use add to effectively replace all values for a given metadata key, by specifying an already-present key as the path, and an array of your replacement values as the value. This use of the add operation to replace a list of values may be counter-intiutive, but it is done according to the RFC section 4.1

If the target location specifies an object member that does exist, that member's value is replaced.

Note:

  • According to the JSON Patch specification, to initialize the first value for any array, the add operation must receive an array of values. Therefore, in the first operation below, since it is not possible to add a single value to the not yet initialized /metadata/dc.description array, we initialize it with an array with one value.
  • When values already exist for a metadata key, as in the second operation below, it is necessary to specify the new value's position at the end of the path (/0 means first position, /- means last).
  • When creating new metadata values, if unspecified, the language and authority properties default to null, and confidence defaults to -1.

Example request, adding three values:

[
  {
    "op": "add",
    "path": "/metadata/dc.description",
    "value": [ { "value": "Some description" } ]
  },
  {
    "op": "add",
    "path": "/metadata/dc.title/0",
    "value": { "value": "Zeroth Title" }
  },
  {
    "op": "add",
    "path": "/metadata/dc.title/-",
    "value": { "value": "Final Title", "language": "en_US" }
  }
]

New metadata state:

{
  "metadata": {
    "dc.description": [
      { "value": "Some description", "language": null, "authority": null, "confidence": -1 }
    ],
    "dc.title": [
      { "value": "Zeroth Title", "language": null, "authority": null, "confidence": -1 },
      { "value": "Initial Title", "language": null, "authority": null, "confidence": -1 },
      { "value": "Final Title", "language": "en_US", "authority": null, "confidence": -1 }
    ]
  }
}

Removing metadata

With the remove operation, you can delete:

  • All metadata with a given key (e.g. path="/metadata/dc.description")
  • A single metadata value with a known position (e.g. path="/metadata/dc.title/0")

When only one value is present for a particular key, it is functionally equivalent to specify the path to the key or the value.

Example request, removing two values:

[
  {
    "op": "remove",
    "path": "/metadata/dc.description"
  },
  {
    "op": "remove",
    "path": "/metadata/dc.title/0"
  }
]

New metadata state:

{
  "metadata": {
    "dc.title": [
      { "value": "Initial Title", "language": null, "authority": null, "confidence": -1 },
      { "value": "Final Title", "language": "en_US", "authority": null, "confidence": -1 }
    ]
  }
}

Replacing metadata

With replace, you can overwrite any of the following within a single operation of a PATCH request:

  • The entire set of all object metadata (path="/metadata")
  • All metadata values for an existing key (e.g. path="/metadata/dc.title")
  • A single existing metadata value (e.g. path="/metadata/dc.title/0")
  • A single property of an existing value (e.g. path="/metadata/dc.title/0/language")

Example request, replacing the value and language of the first dc.title:

[
  {
    "op": "replace",
    "path": "/metadata/dc.title/0",
    "value": { "value": "最後のタイトル", "language": "ja_JP" }
  }
]

New metadata state:

{
  "metadata": {
    "dc.title": [
      { "value": "最後のタイトル", "language": "ja_JP", "authority": null, "confidence": -1 },
      { "value": "Final Title", "language": "en_US", "authority": null, "confidence": -1 }
    ]
  }
}

Ordering metadata

Metadata may be re-ordered with the move operation.

Example request, moving the last dc.title value to the first position:

[
  {
    "op": "move",
    "from": "/metadata/dc.title/1",
    "path": "/metadata/dc.title/0"
  }
]

New metadata state:

{
  "metadata": {
    "dc.title": [
      { "value": "Final Title", "language": "en_US", "authority": null, "confidence": -1 },
      { "value": "最後のタイトル", "language": "ja_JP", "authority": null, "confidence": -1 }
    ]
  }
}