webpub-manifest

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Readium Web Publication Manifest

The Readium Web Publication Manifest is a JSON-based document meant to represent and distribute publications over HTTPS.

It is the primary exchange format used in the Readium Architecture and serves as the main building block for OPDS 2.0.

Example

{
  "@context": "https://readium.org/webpub-manifest/context.jsonld",
  
  "metadata": {
    "@type": "http://schema.org/Book",
    "title": "Moby-Dick",
    "author": "Herman Melville",
    "identifier": "urn:isbn:978031600000X",
    "language": "en",
    "modified": "2015-09-29T17:00:00Z"
  },

  "links": [
    {"rel": "self", "href": "https://example.com/manifest.json", "type": "application/webpub+json"},
    {"rel": "alternate", "href": "https://example.com/publication.epub", "type": "application/epub+zip"},
    {"rel": "search", "href": "https://example.com/search{?query}", "type": "text/html", "templated": true}
  ],
  
  "readingOrder": [
    {"href": "https://example.com/c001.html", "type": "text/html", "title": "Chapter 1"}, 
    {"href": "https://example.com/c002.html", "type": "text/html", "title": "Chapter 2"}
  ],

  "resources": [
    {"rel": "cover", "href": "https://example.com/cover.jpg", "type": "image/jpeg", "height": 600, "width": 400},
    {"href": "https://example.com/style.css", "type": "text/css"}, 
    {"href": "https://example.com/whale.jpg", "type": "image/jpeg"}, 
    {"href": "https://example.com/boat.svg", "type": "image/svg+xml"}, 
    {"href": "https://example.com/notes.html", "type": "text/html"}
  ]
}

1. Introduction

1.1. Goals

While the Web is the largest collection of interlinked documents ever created, it lacks a mechanism for expressing how a collection of resources, when grouped together can represent a publication.

Publication formats such as EPUB or CBZ/CBR group these documents together using a container format, making them easier to archive or transmit as a whole. But they also break an important promise of the Web: the resources of a publication are not available through HTTP to any client that would like to access them.

W3C has recently provided a definition for a Web Publication:

A Web Publication (WP) is a collection of one or more constituent resources, organized together in a uniquely identifiable grouping, and presented using standard Open Web Platform technologies.

It also provides a definition for a manifest in the context of a Web Publication:

[…] manifest refers to an abstract means to contain information necessary to the proper management, rendering, and so on, of a publication. This is opposed to metadata that contains information on the content of the publication like author, publication date, and so on. The precise format of how such a manifest is stored is not considered in this document.

The Readium Web Publication Manifest is an attempt to standardize a JSON based manifest format that follows both definitions.

To facilitate the interoperability between EPUB and Web Publications, this document also defines a number of extension points to fully support EPUB specific features.

1.2. Terminology

Collection
A grouping of some variable number of data items. In the context of this specification, a collection is defined as a grouping of metadata, links and sub-collections.
Full Collection
A collection that contains at least two or more data items among metadata, links and sub-collections.
Compact Collection
A collection that contains one or more links, but doesn't contain any metadata or sub-collections.
Manifest
A manifest is a full collection that represents structured information about a publication.

1.3. Abstract Model

The Readium Web Publication Manifest is based on a hypermedia model inspired by Atom, HAL, Siren and Collection+JSON among others.

Every Readium Web Publication Manifest is a collection that must contain:

2. Syntax

2.1. Sub-Collections

This specification defines two collection roles that are the building blocks of any manifest:

Role Definition Compact Collection? Required?
readingOrder Identifies a list of resources in reading order for the publication. Yes Yes
resources Identifies resources that are necessary for rendering the publication. Yes No

Both collections are full collections, which means that they contain one or more Link Objects.

All additional collection roles are defined in the Collection Roles registry.

Extensions that are not registered in the registry must use a URI for their role.

A manifest must contain a readingOrder sub-collection.

Other resources that are required to render the publication should be listed in resources.

All resources listed in readingOrder and resources must indicate their media type using type.

Example 1: Reading order and list of resources

"readingOrder": [
  {"href": "/chapter1", "type": "text/html"},
  {"href": "/chapter2", "type": "text/html"}
],

"resources": [
  {"href": "/style.css", "type": "text/css"},
  {"href": "/image1.jpg", "type": "image/jpeg"}
]

2.2. Metadata

JSON-LD provides an easy and standard way to extend existing JSON document: through the addition of a context, we can associate keys in a document to Linked Data elements from various vocabularies.

The Web Publication Manifest relies on JSON-LD to provide a context for the metadata object of the manifest.

While JSON-LD is very flexible and allows the context to be defined in-line (local context) or referenced (URI), the Web Publication Manifest restricts context definition strictly to references (URIs) at the top-level of the document.

The Web Publication Manifest defines an initial registry of well-known context documents, which currently includes the following references:

Name URI Description Required?
Default Context https://readium.org/webpub-manifest/context.jsonld Default context definition used in every Web Publication Manifest. Yes

Context documents are all defined and listed in the Context Documents registry.

The Readium Web Publication Manifest has a single requirement in terms of metadata: all publications must include a title.

In addition all publications should include a @type key to describe the nature of the publication.

Example 2: Minimal metadata

"metadata": {
  "@type": "http://schema.org/Book",
  "title": "Test Publication"
}

Links are expressed using the links key that contains one or more Link Objects.

A manifest must contain at least one link using the self relationship where href is an absolute URI to the canonical location of the manifest.

Example 3: Link to the canonical location of a manifest

"links": [
  {
    "rel": "self",
    "href": "http://example.org/manifest.json",
    "type": "application/webpub+json"
  }
]

A manifest may also contain other links, such as a alternate link to an EPUB 3.1 version of the publication for example.

Link relations that are currently used in this specification and its extensions are listed in the Link Relations registry.

The Link Object is a core component of the Readium Web Publication Manifest JSON syntax.

It represents a link to a resource along with a set of metadata associated with that resource.

This specification defines the following keys for this JSON object:

Key Definition Format Required?
href URI or URI template of the linked resource URI or URI template Yes
templated Indicates that href is a URI template Boolean, defaults to false Only when href is a URI template
type Media type of the linked resource MIME Media Type No
title Title of the linked resource String No
rel Relation between the resource and its containing collection One or more Link Relation or URIs (extensions) No
properties Properties associated to the linked resource Properties Object No
height Height of the linked resource in pixels Integer No
width Width of the linked resource in pixels Integer No
duration Duration of the linked resource in seconds Float No
bitrate Bit rate of the linked resource in kilobits per second Float No

3. Resources in the Reading Order

The readingOrder of a manifest may contain references to any text, image, video or audio resource that can be opened in a Web browser.

4. Media Type

This specification introduces a dedicated media type value to identify the Readium Web Publication Manifest: application/webpub+json.

All HTTP responses for the manifest must indicate this media type in their headers.

4. Discovering a Manifest

The Readium Web Publication Manifest may be referenced by resources included in its readingOrder or resources using a link.

Such links must include:

Example 4: Link in HTML to a manifest

<link href="manifest.json" rel="manifest" type="application/webpub+json">

Example 5: Link in HTTP headers to a manifest

Link: <http://example.org/manifest.json>; rel="manifest";
         type="application/webpub+json"

5. Table of Contents

A Readium Web Publication Manifest may contain a reference to a table of contents.

In order to represent a table of contents in the manifest, this specification introduces an additional collection role:

Role Definition Compact Collection? Required?
toc Identifies the collection that contains a table of contents. Yes No

As a fallback mechanism, a Readium Web Publication Manifest may identify an HTML or XHTML resource in readingOrder or resources as a table of contents using the contents link relation.

Example 6: Reference to an HTML resource containing a TOC

{
  "rel": "contents", 
  "href": "contents.html", 
  "type": "text/html"
}

A User Agent may also rely on the title key included in each Link Object of the readingOrder to extract a minimal table of contents.

The EPUB extension also defines additional collection roles for embedding navigation directly in the manifest.

6. Cover

A Readium Web Publication Manifest may contain a reference to a cover.

Link Objects in readingOrder, resources or links can be identified as such using the cover link relation.

All Link Objects containing the cover link relation must reference an image directly. They should include a height and width to facilitate how they are processed by User Agents.

This specification recommends using one of the following media types: image/jpeg, image/png, image/gif or image/svg+xml.

Example 7: Reference to a cover

{
  "rel": "cover", 
  "href": "cover.jpg", 
  "type": "image/jpeg", 
  "height": 600, 
  "width": 400
}

7. Extensibility

The manifest provides multiple extension points:

In addition to these extension points, this specification defines an extension registry as well, to document specific profiles of the manifest.

The initial registry, contains the following extensions:

Name Description
EPUB Extension Additional metadata and collection roles for representing EPUB publications.
Audiobook Profile Defines a dedicated profile for audiobooks.

8. Package

The Readium Web Publication Manifest is primarily meant to be distributed unpackaged on the Web.

That said, a Readium Web Publication Manifest may be included in an EPUB.

If a Readium Web Publication Manifest is included in an EPUB, the following restrictions apply:

Example 8: Reference to a manifest in an OPF

<link rel="alternate" 
      href="manifest.json" 
      media-type="application/webpub+json" />

In addition to the EPUB format, a Readium Web Publication may also be distributed as a separate package where:

Appendix A. JSON Schema

A JSON Schema is available under version control at https://github.com/readium/webpub-manifest/tree/master/schema

For the purpose of validating a Readium Web Publication Manifest, use the following JSON Schema resource: https://readium.org/webpub-manifest/schema/publication.schema.json