Details: Using CrossRef's OpenURL Resolver
OpenURL and CrossRef
In order for information providers to equip their products for optimal integration with library linking systems, they are being asked to implement the OpenURL. This has caused some confusion concerning primary and secondary publishers who use the CrossRef/DOI system for cross-publisher links to full-text, because of the mistaken perception that the OpenURL and the DOI are competing technologies. They are not.
CrossRef and the DOI provide persistent identification of scholarly content and centralized linking to the full text and other resources designated by the publisher. The OpenURL enables library-controlled links to a multiplicity of resources related to a citation and is designed for localized linking. The OpenURL is in fact enhanced by interaction with the DOI system, as explained below.
Some basic definitions
- The OpenURL is a mechanism for transporting metadata and identifiers describing a publication, for the purpose of context-sensitive linking. The OpenURL standard is currently on the path to NISO accreditation. (For more information on the OpenURL, see http://library.caltech.edu/openurl.)
- A link resolver is a system for linking within an institutional context that can interpret incoming OpenURLs, take the local holdings and access privileges of that institution (usually a library) into account, and display links to appropriate resources. A link resolver allows the library to provide a range of library-configured links and services, including links to the full-text, a local catalogue to check print holdings, document delivery or ILL services, databases, search engines, etc.
- CrossRef is a system for the persistent identification of scholarly content and cross-publisher citation linking to the full-text and related resources using the DOI. CrossRef DOIs link to publisher response pages, which include the full bibliographic citation and abstract, as well as full-text access (for authenticated users or at no charge, as determined by the publisher). The publisher response page often includes other linking options, such as pay-per-view access, journal table of contents and homepage, and associated resources. CrossRef is a collaborative membership network, and not a product for purchase.
- DOI stands for Digital Object Identifier and is an open standard. A DOI is an alphanumeric name that identifies digital content, such as a book or journal article. The DOI is paired with the object's electronic address, or URL, in an updateable central directory, and is published in place of the URL in order to avoid broken links while allowing the content to move as needed. DOIs are distributed by publishers and by CrossRef, and there is no end-user charge associated with their use.. As an identifier, the DOI can be incorporated into many different systems and databases. (For more information about the DOI, please see www.doi.org.)
Why libraries need local link resolvers
DOIs point to the authoritative version of content on the publisher's website and to publisher-designated resources. Yet for the user working in an institutional context, it is often useful to be directed to other resources. For example, the institution may not subscribe to the e-journal itself but may still be able to offer the user access to the desired article through an aggregated database or through print holdings. In addition, the library may wish to provide a range of linking options beyond what is available at the publisher's website.
How the DOI and OpenURL work together
The DOI and the OpenURL work together in several ways. First, the DOI directory itself - where link resolution occurs in the CrossRef system - is OpenURL-enabled. This means that it can recognize a user with access to a local resolver. When such a user clicks on a DOI, the CrossRef system does two key things: (1) it redirects that DOI back to the user's local resolver, and (2) it allows the DOI to be used as a key to pull metadata out of the CrossRef database, metadata that is needed to create the OpenURL targeting the local link resolver. As a result, the institutional user clicking on a DOI is directed to appropriate resources. By using the CrossRef DOI system to identify their content, publishers in effect make their products OpenURL aware.
Secondly, since DOIs greatly streamline linking and data management processes for publishers, more publishers are beginning to require that the DOI be used as the primary linking mechanism to full text. Link resolvers can use the CrossRef system to retrieve the DOI, if the DOI is not already available from the source (i.e., citing) document.
In order to take advantage of localized linking, a cookie must be set on the user's machine. For information on the Cookie Pusher script, please see http://www.exlibris-usa.com/sfx_cookiepusher.htm. (Note that the reason this CookiePusher information is available at via SFX is historical, due to their role in prototyping this functionality.)
The value of persistent links
Static URLs are not a persistent linking mechanism. If a URL is published as a link and the content it points to is moved, then that link will no longer function. DOIs address this problem. For instance, the publisher may need to migrate content from one production system to another (pre-print to post-print), or content may move from one publisher to another if a journal, or the publisher itself, changes hands. In these cases the publisher simply updates the DOI directory; the DOI itself never changes, which means that all the links to that content that have already been propagated still function. An OpenURL link that contains a DOI is similarly persistent.
Among the range of linking options they might display, local link resolvers frequently contain links to full-text at the publisher's website, as when the library subscribes to the e-journal in question or otherwise wishes to provide its patrons with access to publisher services and access options. While OpenURLs without DOIs can function persistently if the relevant metadata is updated within the institution's link resolver, this process is greatly streamlined via access to the CrossRef system. CrossRef provides a single source for linking reliably to hundreds of publishers without the need to track varied metadata-based linking schemes. Therefore, link resolvers benefit from using the DOI wherever linking to publisher-designated resources is appropriate.