1. Overview

2. Link Relationships

The following values can be used in the link element rel attribute to establish the relationship of the resource referenced in the href attribute [Packages3].

acquire

The acquire keyword is used with EPUB Previews to identify where the full version of the EPUB Publication can be acquired.

Cardinality:

Zero or more

Example:

<link rel="acquire" href="http://example.org/book/9781448103706" media-type="text/html"/>

alternate

The alternate keyword is a subset of the HTML alternate keyword for links. It differs as follows:

• It cannot be paired with other keywords.
• If an alternate link is included in the Package Document metadata, it identifies an alternate representation of the Package Document in the format specified in the media-type attribute.
• If an alternate link is included in a collection element's metadata [Packages3], it identifies an alternate representation of the collection in the format specified in the media-type attribute.
• Reading Systems do not have to generate hyperlinks for alternate links.

Cardinality:

Zero or more

Example:

<link rel="alternate" href="package.json" media-type="application/json-ld"/>

marc21xml-record [DEPRECATED]

Use of the marc21xml-record keyword is deprecated. It is replaced by the record keyword with the media-type attribute [Packages3] value "application/marcxml+xml".

mods-record [DEPRECATED]

Use of the mods-record keyword is deprecated. It is replaced by the record keyword with the media-type attribute [Packages3] value "application/mods+xml".

onix-record [DEPRECATED]

Use of the onix-record keyword is deprecated. It is replaced by the record keyword with the properties attribute [Packages3] value onix.

record

Indicates that the referenced resource is a metadata record.

The media type of the record is identified in the media-type attribute [Packages3] when this keyword is specified.

For a list of commonly-linked metadata record types, refer to the EPUB Linked Metadata Guide

If the type of record cannot be identified from the media type, an identifier property can be assigned in the properties attribute [Packages3].

Cardinality:

Zero or more

Example:

<link rel="record" href="book/52.atom" media-type="application/atom+xml;type=entry;profile=opds-catalog"/>

xml-signature [DEPRECATED]

Use of the xml-signature keyword is deprecated. It is not replaced by another linking method. Identification of XML signatures will be addressed in a future version of EPUB.

xmp-record [DEPRECATED]

Use of the xmp-record keyword is deprecated. It is replaced by the record keyword with the properties attribute value xmp.

3. Link Properties

The following values can be used in the link element rel attribute [Packages3] to establish the type of record a referenced resource represents. These values are provided for record formats that cannot be uniquely identified by their media type.

onix

The onix property indicates the referenced resource is an ONIX record [ONIX].

Example:

<link rel="record" href="pub/meta/nor-wood-onix.xml" media-type="application/xml" properties="onix"/>

xmp

The xmp property indicates the referenced resource is an XMP record [XMP].

Example:

<link rel="record" href="pub/meta/nor-wood-xmp.xml media-type="application/xml" properties="xmp"/>