Books on Crossref

Deprecating co-access: Crossref plans and timelines

Isaac Farley — Thu, 11 Sep 2025 00:00:00 +0000

To date, there are about 100 Crossref members who have made use of our co-access service for one or more of their books. The service was designed to be a last-resort measure when multiple parties - book publishers, aggregators, and other members - had rights to register book content. Unfortunately, the service allowed members to register multiple DOIs for shared books and book chapters, thereby violating our own core tenet of one DOI per content item. We should not have created a service that violated that tenet, resulting in duplicate DOIs. As we are able to offer an alternative in the form of the multiple resolution service, it is time to switch co-access off. Among other benefits – for the publisher and the authors, creation of a single DOI for each item, regardless of where it might be hosted, will result in more accurate citation counts and usage statistics. We’re retiring co-access at the end of 2026.

An idiom to start

There’s an idiom used in technology circles called ‘eating your own dog food.’ It’s used to describe an organization that tests or uses its own products in the real world. I’m no developer and only have a handful of years of exposure to this phrase, but I’ve always wanted to work it into one of my blog posts. The visceral reactions I have observed when it’s been used on internal calls are just too tempting. That, and I think it applies to our own rollout of and missteps with a service we call co-access. The decision to enable co-access reflected the priorities of that period, but we can now improve on it with an upgraded multiple resolution service. That rickety footing for co-access doomed it from the start. Now’s the time to face the music and swallow our own kibble.

Always meant as a last-resort measure, co-access allows multiple Crossref members to register metadata for shared book and book chapter content. Thus, use of co-access results in multiple, duplicate DOIs registered for the same book content. There are well over 500,000 DOIs in co-access within our corpus today. At least half of those are duplicates (more on this below).

This is far from ideal and has adverse consequences for the integrity of the scholarly record and the community. As we are able to offer an alternative in the form of the multiple resolution service, it is time to switch co-access off.

Among other benefits – for the publisher and the authors, creation of a single DOI for each item, regardless of where it might be hosted, will result in more accurate citation counts and usage statistics.

Duplicate DOIs

We frequently receive questions from members, metadata users, and others in the community, like this one, asking us what we are doing to combat the very real problem of registration and propagation of duplicate DOIs. We do take measures to prevent the registration of duplicate DOIs, including flagging registration of potential duplicate records to our members using what we call conflicts and conflict reports. As you might expect, this has been a sensitive topic for us, because we have one glaring service, yes, co-access, that has been actively exacerbating the issue of duplicate DOIs.

So, while we have been actively trying to counter the rise of duplicate DOIs, co-access enabled duplicate registrations of book DOIs. For every prefix that we configured for the service, we knew we were contributing to the problem (our members noticed too. As I said above, co-access allows multiple members to register their own DOI for shared book content. That means that book content in co-access has at least two DOIs registered. In some cases, there is book content with five or more registered DOIs for a single book. That’s a great many duplicates that this service is responsible for.

Replacing co-access

We plan to replace co-access with an existing tool, multiple resolution, which allows for more than one resolution URL to be registered to a single DOI. A user resolving the DOI is presented with an interim page, allowing them to choose from the various content sources registered with this DOI. We’ve made some progress toward making multiple resolution simpler for members to implement, but we still have more to do.

We’re aware that the technical steps involved in adopting multiple resolution might present a barrier to implementation for some of our members. To help with the transition, we are working on a basic tool (currently in beta) that simplifies the process. We will make it available to members between now and the middle of 2026.

Our timeline

We are not going to make these changes tomorrow. We’re going to give members who have been using co-access time to adjust. Right now, we trigger co-access when a secondary DOI is registered by a secondary registrant (member) that: 1) is already in a co-access group within our system with the DOI prefix that registered the original DOI, 2) has at least one shared ISBN with the metadata of that original DOI, and 3) has a title (in the title element of the book or chapter XML) that exactly matches the title of the original DOI. We’re going to stop triggering co-access for book and book chapter registrations starting 2026 July 1. No new DOIs will be placed in co-access starting then.

From there, there will be six months to clean up records already in co-access. One definitive DOI should be selected by the parties in a co-access group; the DOIs that will no longer be maintained for those books and book chapters should be aliased to the primary (definitive) DOI that will be maintained going forward. The primary DOI should be the DOI used on all landing pages for that book (or, book chapter).

In January 2027, if co-access DOIs have not been aliased to one another, we will force alias the DOIs in the record to the DOI registered by the organization identified as the publisher in the metadata records already in our system. At any point in this timeline, our team will be happy to help with the registration of secondary URLs in order to move books from co-access to multiple resolution. As a result, we will encourage members, end users, and the broader community to move back to using a single, definitive source of truth for these books and book chapters.

What will registration of books and book chapters look like post-co-access?

Coordinated. We expect that our members and their publishing partners will define the single DOI for each book and book chapter well upstream of Crossref, so all entities and their systems will use that one definitive DOI.

As for the registration process and our system, the first member to register the book (and its ISBNs) will establish the DOI for that book and its chapters. Following attempts to register the same content, with a duplicate book-level DOI(s), will fail the registration. Multiple DOIs for the same book or book chapter should be avoided starting 2026 July 01, as we will no longer be able to place books and book chapters into co-access.

We believe this will result in increased cited-by and usage metrics for that single DOI, and a cleaner, more accurate scholarly record.

We’d love to hear your reaction to this news in our Community Forum.

Measuring Metadata Impacts: Books Discoverability in Google Scholar

Lettie Conrad — Wed, 25 Jan 2023 00:00:00 +0000

This blog post is from Lettie Conrad and Michelle Urberg, cross-posted from the The Scholarly Kitchen.
As sponsors of this project, we at Crossref are excited to see this work shared out.

The scholarly publishing community talks a LOT about metadata and the need for high-quality, interoperable, and machine-readable descriptors of the content we disseminate. However, as we’ve reflected on previously in the Kitchen, despite well-established information standards (e.g., persistent identifiers), our industry lacks a shared framework to measure the value and impact of the metadata we produce.

In 2021, we embarked on a Crossref-sponsored study designed to measure how metadata impacts end-user experiences and contributes to the successful discovery of academic and research literature via the mainstream web. Specifically, we set out to learn if scholarly books with DOIs (and associated metadata) were more easily found in Google Scholar than those without DOIs.

Initial results indicated that DOIs have an indirect influence on the discoverability of scholarly books in Google Scholar – however, we found no direct linkage between book DOIs and the quality of Google Scholar indexing or users’ ability to access the full text via search-result links. Although Google Scholar claims to not use DOI metadata in its search index, the results of our mixed-methods study of 100+ books (from 20 publishers) demonstrate that books with DOIs are generally more discoverable than those without DOIs.

As we finalize our analysis, we are sharing some early results and inviting input from our community. What relevant lessons can we glean from this exercise? What changes might book publishers consider based on the outcomes of this study?

Background on the study

This study was designed to evaluate metadata impacts & benefits to users. Given its popularity with a range of stakeholders in our industry, we set out to measure metadata impacts on discoverability in the mainstream web – namely, Google Scholar.

Our test method and analysis rubric was developed based on our own information-user research, in particular how readers search and retrieve scholarly ebooks, as well as published studies about academic information experiences and research practices. We rated the search performance of more than 100 scholarly books using preset test queries (two for each title). The books tested in this study came from publishers of all sorts and sizes, and represent both monographs and edited volumes from a range of fields; some were open access and others were published under traditional licensing models.

We developed and executed known-item test searches that were designed to simulate common researcher practices. Heuristic analysis of the search results was used to rate the search performance on a 5-point scoring rubric, which was designed to measure the degree of friction in locating the book in question. This method allowed us to assess specific book and metadata attributes by their search performance scores to assess the impact of book metadata on content discoverability in Google Scholar.

Results and findings

In this study, we learned that high-value fields include the primary title paired with subtitles, author/editor surnames and/or field of study. Queries using full book titles performed the best across the board. Those using publication dates and/or author/editor surnames and/or publisher names, but without the book title, were the lowest performers.

Surprisingly, our discoverability scores show no significant variation in performance by the type of book, whether edited or authored. Open-access titles performed somewhat better than traditional ones. Books covering humanities and social science fields performed a bit better than STM books, but only by a slim difference (that is not statistically significant).

We primarily tested the discoverability of book titles, from equal numbers of books with and without chapter-level DOIs. We ran similar tests for chapter-title discoverability but found the majority of test queries for chapters lead users to the full book itself. While books without title-level DOIs were found to be less discoverable, we did not find a measurable difference between books with or without chapter-level DOIs. (Note: All books in this study with chapter-level DOIs assigned also carried a title-level DOI, which was found to be fairly common.)

Based on these results, we are developing a theory that books with DOIs perform better in Google Scholar because they benefit from the structured, open metadata associated with those DOIs – which are used by hundreds of platforms and services, and therefore are “seeded” throughout the mainstream web, which Scholar may draw on for indexing, linking, etc. That said, however, these results also suggest that publishers are best served by a metadata strategy that is well attuned to the protocols expected of each channel for book search and discovery. In a recent conversation about our findings, Anurag Acharya himself noted that these results underscore the need for publishers to invest in the robust construction and broad distribution of book metadata.

In this study, we have observed that the metadata protocols surrounding Google Scholar are not fully integrated into our industry’s established scholarly information standards bodies, like NISO, or infrastructure organisations, like Crossref. While some mainstream data standards prevail in the Scholar index, like the use of schema.org and HTTP, some key metadata attributes seem to be lacking. For example, an indicator of the type of scholarly book (monograph, handbook, etc.) would improve Google Scholar’s search index and could be used to filter search results, thereby improving users’ experiences discovering scholarly books. One clear challenge for book publishers today is the fact that Google Scholar operates outside of our community-governed scholarly information infrastructure.

What comes next

While this study focused on Google Scholar, the results and lessons learned are applicable to other mainstream channels of information seeking/discovery. Our report, due out spring 2023, will contribute to the literature intended to support user-centric information systems design and content architecture by scholarly publishers and service providers.

As we write up our findings, we intend to develop a framework that can help publishers and others measure the impact of their work to enrich and distribute scholarly metadata. We hope this first systematic review of the impacts of metadata on the discoverability of books in Google Scholar will provide valuable insights for this community. In the meantime, please share your thoughts and questions in the comments below – or reach out to us directly (see Lettie’s profile here and Michelle’s profile here).

Acknowledgments: The authors would like to thank Jennifer Kemp at Crossref for the inspiration to take this dive into the metadata literature and reflect on its impact on research information experiences. Special thanks to Anurag Acharya at Google Scholar for his consultation during this study.

Good, better, best. Never let it rest.

Jennifer Kemp — Tue, 16 Oct 2018 00:00:00 +0000

Best practices seem to be having a moment. In the ten years since the Books Advisory Group first created a best practice guide for books, the community beyond Crossref has developed or updated at least 17 best practice resources, as collected here by the Metadata 2020 initiative. (Full disclosure: I co-chair its Best Practices group.)

Books have been one of the fastest growing resource/record types at Crossref for some time, and best practices are just one of the Book Advisory Group’s efforts. Over the past ten years, the members of the books group have updated and added to the guide, and it’s now time for it to get some visibility, so we have added it to our website for easy reference.

These best practices are not documented for the sake of it. They have real value and can help guide internal conversations to evaluate current practices, for example. They can also play a role in making or changing policies, training staff and providing instructions to authors on citation formatting.

Here are a few recent changes I’d like to highlight:

A new section has been added that addresses books hosted on multiple platforms
The section on versions, (including books in multiple formats) has been expanded and clarified
A section on the use of DOIs in citations has been added

It is neither final nor comprehensive, and never will be. Best practices by their very nature must evolve over time—and those with such a broad scope as books will inevitably lack some detail—but that’s all the more reason for the community to stay engaged. Looking ahead to future work from the group, chapter-level metadata is likely to get more attention.

Over the past few years the Books Advisory Group, chaired with aplomb by Emily Ayubi of the American Psychological Association (APA), has spent a lot of time on Crossref initiatives, like Multiple Resolution and DOI display changes but also on broader industry topics like ORCID iDs for book authors, and the Books Citation Index.

As Emily’s term as chair comes to an end this year, we welcome Charles Watkinson of the University of Michigan as chair starting in 2019. The group meets next on 12 December when we will hear from Coko about Editoria and have a discussion about developing our new Metadata Manager Content Registration tool for books, and more.

If you want to share your thoughts on best practices or if you have other topics you’d like us to consider, please get in touch.

Revived: Crossref Books Interest Group

April Ondis — Wed, 24 Feb 2016 00:00:00 +0000

We’re reviving the Books Interest Group, and inviting new members!

After a hiatus, Crossref’s Books Interest Group is back. We’re excited to announce that Emily Ayubi of the American Psychological Association has agreed to chair the group.

In reviving the group, our intention is to create opportunities to talk about issues that are important to scholarly book publishers. For example, we hope to explore whether it is time to revise the Crossref best practices for depositing, versioning, and linking book content.

We are seeking interested members from the book publishing community, and want to hear your ideas for agenda items and topics for discussion.

Our first meeting will be a teleconference held at 11:00 am Eastern time on Wednesday, March 23rd. You will receive dial-in details by email. ** **

If you’d like to join—and we’re hoping you will—please email me at aondis@crossref.org.