The Crossref Curriculum

The structure of a DOI

A DOI (digital object identifier) is a persistent identifier attached to content (such as an article, chapter). It’s displayed as a link, and looks like this:

The structure of a DOI: resolver, prefix, suffix

As you can see, it has several parts:

  • https://0-doi-org.libus.csd.mu.edu/ = the DOI resolver: makes the DOI a URL (actionable)
  • 10.5555 = prefix: assigned by Crossref
  • YFRU1371 = suffix: decided and assigned by the member, should be opaque.

The prefix and suffix make a DOI, and with the DOI resolver form a DOI link.

As we mention above, the suffix should be opaque. An opaque identifier does not encode or describe any information about the work, such as publication name, date, or ISSN. It’s important to avoid encoding any human-readable information, so if any of the metadata associated with the DOI changes, there is no confusion between the information encoded in the DOI and that found in its metadata.

For example, 10.5555/njevzkkwu4i7g is opaque, but 10.5555/ogs.2016.59.1.1 encodes information which may change and therefore could be confusing or misleading in future.

Learn more about display guidelines for Crossref DOIs.

The DOI link uses the DOI resolver to look up the registered URL for the item. This shows why it’s important to keep the metadata up-to-date, so that the DOI points to the correct URL for the item.

DOIs at different levels

A DOI may refer to a journal or book (a title-level DOI), or to a specific article or chapter.

Like a set of nesting dolls, a journal may be made up of volumes, issues, and articles

Journals and DOIs

Like a set of nesting dolls, a journal may be made up of volumes, each containing a number of issues, each containing a number of articles. You can assign a DOI at each level, for example:

  • journal-level-DOI (sometimes called the title-level-DOI) 10.5555/QYPF2031. Like an ISSN, it refers to the whole journal
  • volume-level-DOI 10.5555/FFFU4804
  • issue-level-DOI 10.5555/QKLE5634
  • article-level-DOI 10.5555/CNBT7653

The role of the journal-level-DOI, volume-level-DOI, and issue-level-DOI is to link persistently to a point in the journal structure. These DOIs do not have any associated content, and it does not cost anything to register these DOIs.

However, article-level-DOIs do have associated content, and therefore a fee applies to register these DOIs.

Books and DOIs

Like a set of nesting dolls, a book may be made up of chapters. Again, you can assign a DOI at each level, for example:

  • book-level-DOI (sometimes called the title-level-DOI) 10.5555/ZAAR1365. Just like an ISBN, it refers to the whole book.
  • chapter-level-DOI 10.5555/TFWD2627

Both book-level-DOIs and chapter-level-DOIs have associated content, and therefore a fee applies to register these DOIs.

Learn more about our fees for different content types, and how to construct your DOIs.

Page owner: Laura J. Wilkinson   |   Last updated 2020-April-08