In this section we cover what it means for technology to be interoperable using OpenURL link resolvers.


We take it for granted that, on the open web, we can seamlessly follow links to websites and webpages, or do so without too much fuss. It gets more complicated when we want access to works that are behind paywalls, despite where such works have been found: search engines, bibliographic databases, OPACs, or discovery services. In such cases, direct links to such sources will not always work.

The complication is that, when a library subscribes to a journal or a magazine, access to that journal or magazine is provided through various services and not necessarily through the publisher's default site. Also, libraries provide multiple discovery points and multiple ways to access the same works, such as through bibliographic databases with overlapping scopes. Bibliographic databases can tell us that an item exists when we search for it, but a library may not subscribe to the publication or the item might be in the stacks, stored off site or at another library altogether. All these problems, in conjunction with the paywalled problem, which necessitates additional layers, like proxy servers that function to authenticate library users, complicate access.

Let's consider an example. The journal Serials Librarian is published by Taylor & Francis Online / Routledge, and has the following site as its homepage:

The journal is indexed in EBSCOhost's Library, Information Science & Technology Abstracts (LISTA) database and in ProQuest's Social Science Premium Collection (SSPC) database, among other places (e.g., it can also be found in Google Scholar, Google Search, a library's discovery platform, and more). This means that an article like the following can show up based on a query on any of the above platforms, even if none of these search or discovery platforms provide full text access to the article:

Brown, D. (2021). "Through a glass, darkly:: Lessons learned starting over as an electronic resources librarian. The Serials Librarian, 81(3–4), 246–252.

One way to know if our library provides access to the above source and others like it is through a link resolver. We see UK's link resolver in action whenever we see a View Now @ UK button or link. When we click on that button or link in someplace like LISTA or SSPC, we trigger the database's role in the link resolver for that article, and that routes us through the library's discovery service. In LISTA, that link looks like this:

In Social Science Premium Collection, the link looks like this:$2f$$2fopenurl$2f01SAA_UKY$2f01SAA_UKY:UKY$3furl_ver$3dZ39.88-2004$26rft_val_fmt$3dinfo:ofi$2ffmt:kev:mtx:journal$26genre$3darticle$26sid$3dProQ:ProQ$253Alibraryscience$26atitle$3d$2526ldquo$253BThrough$2ba$2bGlass$252C$2bDarkly$2526rdquo$253B$253A$2bLessons$2bLearned$2bStarting$2bover$2bas$2ban$2bElectronic$2bResources$2bLibrarian$26title$3dThe$2bSerials$2bLibrarian$26issn$3d0361526X$26date$3d2021-11-01$26volume$3d81$26issue$3d3-4$26spage$3d246$26au$3dBrown$252C$2bDaniel$26isbn$3d$26jtitle$3dThe$2bSerials$2bLibrarian$26btitle$3d$26rft_id$3dinfo:eric$2f$26rft_id$3dinfo:doi$2f10.1080$252F0361526X.2021.2008581/MSTAR_2645781371/LinkResolver/1193?t:ac=2645781371/Record/D137B205B8D14795PQ/1

Clicking on either of the above in their respective databases will send us to Primo, UK Library's discovery layer.

If we had clicked on EBSCOhost's View Now link, the Primo link will result in the following:,%20Darkly%22:%20Lessons%20Learned%20Starting%20over%20as%20an%20Electronic%20Resources%20Librarian.&sid=EBSCO:Library,%20Information%20Science%20%26%20Technology%20Abstracts:156075536&volume=81&pages=246-252&issn=0361526X&au=Brown,%20Daniel&genre=article&ID=doi:10.1080%2F0361526X.2021.2008581

If we look closely at those links (scroll to the right to view their entirety), you can see that the article's metadata is embedded in the URLs. Among other things, you can see the publication title, the article title, the author's name, the DOI, and more.

That metadata is used to trigger a search query in the library's discovery platform (at UK, that's InfoKat Discovery by Primo). It specifically initiates a GET HTTP Request, which is designed to request data from a resource/server, in this case InfoKat Discovery, using the metadata embedded in the URLs as seen above.

This is the work of an OpenURL link resolver, among other technologies, which are designed to provide access to a target despite their source by initiating queries in an OPAC or discovery platform using the metadata embedded in a URL.

This is a technical solution to the paywall problem that is designed to help users of electronic resources access a source in a library's collection based on a citation/record discovered in a search result, an article's list of references, or wherever else the link resolver might show up. It is meant to work for all items in a library's collection, including print items, since print items have records in the catalog or discovery service.

Use Cases

Google Scholar Example

Let's imagine a search in Google Scholar, and that as a result of this search, we identify a paywalled article that we wish to retrieve from the library. If we have made Google Scholar aware that we are affiliated with a specific library, by that affiliation Google Scholar becomes aware of a library's collections (through a knowledge base). Then Google Scholar will use a library's link resolver service to retrieve a target from a library's collections using the following process:

  1. The metadata about the article will be extracted from Google Scholar (aka, the source).
  2. More metadata will be added about the institution (administrative metadata, like an institutional ID number).
  3. The metadata is converted into a URL query that queries the library's collections in the discovery service, and
  4. The user is then presented with target options (or taken directly to the work) for retrieving the article.
    • the options may include full text access from various and possibly multiple vendors or publishers, information about the physical location (e.g., on the shelves) if it exists there, or options to request the work through interlibrary loan. Ideally, it will lead the user directly to the full text.

To link Google Scholar to an affiliation:

  1. Go to
  2. Open Settings
  3. Click on the Library Links tab
  4. Search for your affiliation
    • e.g., University of Kentucky
  5. Add and save

Now when you search in Google Scholar, you should see View Now @ UK links (if your affiliation is University of Kentucky) next to search results that your affiliation has in its collections.

See Link Resolver 101 for additional details and this historical piece on link resolvers (McDonald & Van de Velde, 2004).

Consider a basic keyword search in Google Scholar for the term electronic resources. One of the first items listed in the results page is an article titled "Electronic resources: access and usage at Ashesi University College." If we've connected our library to Google Scholar, then we should see a View Now @ UK link to the right of our search result list. In the following OpenURL, we can see the article's metadata and also that google is the source (just as we could see that ebscohost and proquest were the sources in the URLs above).

Full text for that article is provided by Emerald eJournals Premier, and Emerald is the original publisher of this journal and provides the original view of the article. That means that Primo next hands off our query to UK Library's proxy service, EZProxy, which asks us to authenticate ourselves with our university account login information, and then takes us to a copy of that full text from the provider. The article is also available as full text through two ProQuest databases, but Emerald's view takes precedence since it's the original publisher.

If other resources provided access, like the EBSCOhost and ProQuest databases, and not the original publisher, like Emerald, we would stop on Primo and be offered to select which database we would like to use to view the full text.

In our case, since we only have one option, the Primo to EZProxy to the Emerald full text view transfers happen quickly.

Dissecting an OpenURL

Let's take a closer look at the Primo URL. By looking at its components, we see that it's an OpenURL link, and we can see the fields and values and identify the metadata. The percent signs and numbers in the title field use Percent-encoding. Percent-encoding is a process used to encode characters that are URL unfriendly, like empty spaces between words, into characters that can be parsed. See this page for a table of UTF-8 percent-encodings and the characters they match. I have inserted newlines into the Primo link below to enable readability:

The link resolver technology translates the metadata embedded in the above link as needed for the appropriate service. The institution, vid, and sid fields are administrative metadata that identify the source information. The key fields used to retrieve the record for this source are the:

  • aulast for author's last name
  • id for the DOI
  • auinit for the author's first two initials
  • atitle for the article title

In Case of Interlibrary Loan

We can see another instance of this within Primo itself. Here I search for the phrase electronic resources and filter by WorldCat options from the drop down box to the right of the search box. By filtering for WorldCat options, I'm more likely to retrieve records that are not in UK Library's collections.

The first option is a work titled Electronic Resources. Selection and bibliographic control. Since this is not available via UK Libraries, I would have to request the item through interlibrary loan. When I do that, the link resolver triggers ILLiad, which is used for interlibrary loan. Note how the OpenURL looks much different here. Essentially, the OpenURL is contextual, and its context reflects the service being used (i.e., EBSCOhost, ProQuest, Google Scholar, Primo, Illiad, etc.) which determines the metadata elements in the URL. Note that some elements are empty (e.g., is an empty value for the date field versus rft.genre=book&, which holds the value book for the genre field).


Our readings this week by Kasprowski (2012), Johnson et al. (2015), and by Chisari et al. (2017) discuss link resolver technology, migration to new link resolver services, and methods to evaluate link resolver technology from both the systems and a user's perspective. It may not be necessary to learn how to hack your way through the OpenURL syntax, as I have above (or below: See Appendix A), or other aspects of link resolver URL formatting, but it is a good idea to acquire a basic understanding of how the URLs work in this process.

Let me re-emphasize that the key way that link resolvers work is by embedding citation metadata within the link resolver URL, including administrative metadata. This is another reason to have high quality metadata for our records, as our readings note. By implication, if we find, perhaps by an email from a library patron, that a link has broken in this process, it might be that the metadata is incorrect or has changed in some important way. Knowing the parts of this process aids us in deciphering possible errors that exist when the technology breaks.

For this week, see the ExLibres Alma link resolver documentation, which is the link resolver product used by UK Libraries. Let's discuss this documentation in the forum. I want you to find and explain other instances of link resolvers. Be sure to provide links to these examples and articulate ways the technology can be evaluated.

Documentation to read and discuss:

Link Resolver, Usage

Additional information

Appendix A

How I Enhanced Zotero by Hacking OpenURL

Since OpenURL compatible link resolver technology is partly based on query strings, as we have seen, we can glean all sorts of information by examining these URLs: the query string component that contains the metadata for the source but also the base component that contains the vendor and institutional information and also the URL type. When I worked on this section, I was able to learn that Primo/Alma uses two URL types to request resources: a search URL and an OpenURL. We can see this the URLs. The base search URL looks like this:

The base OpenURL differs just a bit (see the end of the URL):

The base search URL appears when searching the university's discovery service. However, the OpenURL only appears when needed and during transit between the source and before reaching the target: e.g., after clicking on a View Now @ UK link and before being redirected to the full text version. I copied my institution's specific OpenURL when I clicked on a View Now @ UK link and before it redirected to the EZproxy page.

My students often identify great problems to solve or are the source of great ideas. In a previous semester, one of my students in my electronic resource management class noticed that Zotero has a locate menu that uses OpenURL resolvers to look up items in a library. By default, Zotero uses WorldCat, but it can use a specific institution's OpenURL resolver. I had completely forgotten about this. When I investigated whether my institution was listed in the Zotero locate menu, I found that it was not nor was it listed on Zotero's page of OpenURL resolvers.

At the time, I didn't know what my institution's exact OpenURL was, but I was able to figure it out by comparing the syntax and values from other Primo URLs listed on Zotero's page of OpenURL resolvers. By comparing these OpenURLs, I was able to derive my institution's specific OpenURL (base component plus institutional info), which is:

I added that to Zotero, and it worked, and then I posted the OpenURL info to Zotero's forum, and they've added it to their OpenURL resolver page. If others are curious about how to add this info to Zotero, another library has created a video on this. The directions cover adding a specific OpenURL to Zotero and on how to use Zotero's Library Lookup functionality.

Appendix B

A Basic URL

I mentioned query strings above. Theses are a part of a URL that include instructions to query engines, database, or websites (like Wikipedia). The parameters (i.e., search terms) are part of a query string, too. It's also important to understand the base part of a URL (link) because the link in link resolver is the part of the whole process. A URL for an article can looks like this:

This URL contains the following components:

  • https:// : indicates the secure hypertext transfer protocol (HTTP)
  • www : indicates the subdomain
  • emerald : indicates the second level domain name
  • .com : indicates the top level domain

Under a standard configuration, the rest of the URL indicates directory (or folder) location information on the server. The following suggests that the article is seven directories (or folders) deep on the server:

  • /insight/content/doi/10.1108/10650740510632208/full/html

The DOI (digital object identifier) for this article is part of the above URL and is specifically 10.1108/10650740510632208. The DOI is composed of a prefix and a suffix. The prefix includes the following elements:

  • 10 : this is the directory indicator
  • 1108 : the registrant code for this specific journal

The suffix refers to the following element:

  • 10650740510632208 : a character string (in this case, of numbers) that refers to the article. This string is created by the registrant

The DOI itself can be used to create a permanent URL for the above work be adding a to the beginning:

Readings / References

Chisare, C., Fagan, J. C., Gaines, D., & Trocchia, M. (2017). Selecting link resolver and knowledge base software: Implications of interoperability. Journal of Electronic Resources Librarianship, 29(2), 93–106.

Johnson, M., Leonard, A., & Wiswell, J. (2015). Deciding to change OpenURL link resolvers. Journal of Electronic Resources Librarianship, 27(1), 10–25.

Kasprowski, R. (2012). NISO’s IOTA initiative: Measuring the quality of openurl links. The Serials Librarian, 62(1–4), 95–102.

Additional References

McDonald, J., & Van de Velde, E. F. (2004, April 1). The lure of linking. Library Journal. Library Journal Archive Content.