In the same way footnotes and bibliographies lead us from article to article in the print world, hyperlinked references guide us from ebook to ebook or article to article in the electronic world. While this type of linking has existed within WESTLAW or LEXIS, it is relatively new to e-journal publishing, where articles cite works published by different vendors, e-journals located in licensed aggregator databases, or print items in library catalogs that do not yet exist in digital formats. Seamless, transparent navigation between citations is difficult to build in this barrier-ridden environment.

As the journal publishing world moves to embrace a fee based article economy these barriers begin to break down. Researchers pursue citations primarily by title or author rather than journal name. This makes direct linking between citations and the referenced work a primary conduit for tracing research. These reference links are being built with Digital Object Identifiers (DOIs). DOIs provide a framework for managing intellectual content, for linking customers with content suppliers, for facilitating electronic commerce, and enabling automated copyright management for all types of media. Using DOIs makes managing intellectual property in a networked environment much easier and more convenient, and allows the construction of automated services and transactions for e-commerce. One of the only full implementations of the DOI system, CrossRef, is now just over a year old.

CrossRef is a collaborative effort of several scholarly publishers. It enables links from reference citations within articles or bibliographies to the content cited by those references regardless of whether the content is located on a different server or published by a different vendor. According to Amy Brand, CrossRef's Director of Business Development, CrossRef aims to become nothing less than the complete reference-linking backbone for all scholarly literature in electronic form.

There are no fees for following links enabled by CrossRef. Users clicking on a CrossRef enabled citation will see at least a full bibliographic citation. Access to the abstract and full text article is determined by each publisher's own access control system. Information on how to acquire an article will be provided (such as by subscription, document delivery, or pay-per-view, etc.). Each participating publisher is free to set their own access standards and conditions. The service is based on a prototype developed by Wiley and Academic Press, and was developed in cooperation with the International DOI Foundation, building on work by the Association of American Publishers (AAP) and the Corporation for National Research Initiatives (CNRI).

Participating publishers have formed the Publishers International Linking Association, Inc. (PILA), a not- for-profit membership corporation managed by an elected Board. PILA is responsible for running the CrossRef service and developing enhancements to the technology.

CrossRef has grown to include 70 leading journal publishers, both commercial and non-profit, with over three million deposited records from 3,875 journals. The system is on track to add between 500,000 and one million new records per year.

Brand describes CrossRef as a process, not a product. Each member creates a DOI incorporating their own DOI prefix for each journal article, tagging it to metadata and a URL. These resulting records are then submitted to the CrosRef metadata database (MDDB) in XML. CrossRef then registers each article DOI and URL in a central DOI directory. Publishers can insert CrossRef links into any of an article's citations that point to content already registered in the CrossRef system.

The CrossRef system uses open standards and employs a uniform set of rules to accommodate the publishers right to control their business policies and maintain branding, while allowing the researcher to navigate through the widely distributed content of multiple publishers. The rules cover what can be named by a DOI, what types of data can be stored in the DOI System, and the way prefix holders can use DOIs on the web. A researcher clicking on a CrossRef link will be connected to a page on the publisher's website showing a full bibliographic citation of the article, and, in most cases, the abstract as well. The reader can then access the full-text article. While subscribers can generally go straight to the text, non-subscribed users are presented with options for access.

One problem the system does not yet address for libraries is the appropriate copy issue. This involves directing the user to the local subscription rather than asking them to pay a fee to the publisher for retrieving an article. Resource discovery services must be able to authenticate subscribed or licensed users somewhere in the process and ensure that a given user is accessing as a default the version of an article that their library may have already paid for. While CrossRef is developing a localized linking feature to address this, it will only deal with electronic items. An ideal solution would also allow the library to incorporate references to print and microform collections as well. A system such as the one illustrated by CrossRef that would allow users access to a library's electronic subscriptions and hooks into the library catalog for print and microform holdings would go far in saving the time of the user.

It does beg the question of how systems like this and the library catalog work together. We typically do not catalog journals at the article level, but it is clear that researchers are used to accessing information at that level and the ejournal marketplace is responding. Will the two systems converge or will one be left behind? While digitization initiatives are gaining speed, their content is not universal. Archiving, incomplete data and other issues also abound. There are issues related to item description as well. Just as cataloging is more than MARC, metadata is more than XML. The MDDB records in systems such as CrossRef may not be up to library cataloging standards. Do they need to be? If viewed as an access system still in its infancy, CrossRef shows a great deal of promise and presents an example of how new economic models for journal publishing are converging with new means of accessing and managing information. It also raises interesting questions of how systems for accessing our hybrid libraries of print and digital information may develop.

For More Information:

Brand, Amy
CrossRef Turns One. D-Lib Magazine (v. 7, no. 5)
http://www.dlib.org/dlib/may01/brand/05brand.html

CrossRef
http://www.crossref.org