In UK Higher Education the online catalogue (OPAC) of the library system has been largely replaced by discovery services. These link to the print collection and index electronic resources (typically journal articles). As well as the library catalogue a discovery service may 'harvest' (usually by the OAI-PMH) metadata from other repositories. Discovery services solutions are made up of:

• A central index of electronic resources (subscription and open access)
• A knowledge base which defines what resources (including the components of a 'package' or resources) are subscribed to by the library
• A link (usually OpenURL) resolver to enable the authenticated an authorised library user to access subscribed resources without hitting a paywall

A Higher Education Library Technology (HELibTech) webinar 23 July 2024. Link to the recording

The fundamentals of library discovery services have been well-established for over a dozen years, and the landscape is dominated by a few key players. The major discovery services will need to be more strongly differentiated than the alchemy that determines the relevance ranking of the results. The potential of AI to reinvigorate library discovery services has generated much discussion. This webinar goes beyond discussion, theory, and speculation to reveal a real working implementation of AI in an innovative library discovery solution that is available now. It shows how AI enriches the discovery experience to better meet the needs of students and researchers.

(TDNet AI is a library discovery service powered by Generative AI . TDNet AI draws on content included in TDNet Index, featuring over 550 million scholarly information resources from a variety of reputable publishers.By harnessing to power of Natural Language Processing and Artificial Intelligence, TDNet AI allows users to input search queries in everyday language without worrying about specific keywords or Boolean operators. TDNet AI identifies relevant results from the TDNet Index, understanding the intent and meaning behind the search. Additionally, TDNet AI synthesizes key findings from the top search results into concise summaries, complete with references and links to relevant articles.)

Thinking the unthinkable – doing away with the library catalogue**. Simone Kortekaas Bianca Kramer UKSG Insights Volume: 27 Issue: 3 Pages : 244-248 2014 . DOI: 10.1629/2048-7754.174

“At Utrecht University we strongly believe that academic libraries have lost their role in the discovery of scientific information and should focus on delivery instead. Without your own discovery tool you might feel stark naked. However, we have to admit that others can do a better job on discovery, so don’t spend too much time on this. Make a priority of your delivery task and rethink the way you can provide value for your users.”

“From international studies we have learned that students and scholars are moving away from library websites and online library catalogues. Most students start their search in a general search engine on the web and don't use the library website as a starting point. Scholars use specific research databases and they also use general search engines on the web.

Since scholarly information can increasingly be found via publicly accessible search engines (like Google Scholar) and via paid multidisciplinary and subject-specific search engines, and students and staff are increasingly taking that route>”

See also the plenary presentation at the 2014 UKSG conference
'Thinking the unthinkable - doing away with the library catalogue' By Simone Kortekaas Utrecht University.

The discovery solutions and public catalogue (OPAC) products (and vendors) used by UK HE institutions are listed on the Library technology in UK HE - who has which systems page

• EDS (Ebsco Discovery Services). Works with a variety of library systems
• Primo . (Ex Libris/Clarivate). Works exclusively with the Alma library services platform
• Summon (ProQuest/Clarivate).Works with a variety of library systems
• WorldCat Discovery (OCLC). Works with the OCLC WMS library system
• TDNet Discover AI (TDNet) Works with a variety of library systems

Encore**: (Innovative Interfaces/Clarivate). The discovery solution for the Sierra library system. It does not include a central index of electronic resources

Prism**: ESS -was Capita. The discovery solution for the ESS library system. It does not include a central index of electronic resources

Aspen**; an open source discovery solution. It does not include a central index of electronic resources

Explorit: (Amplyfi). A federated search (ie it does not have a central index by instead send search request to the appropriate databases) tool that provides access subscription, public, and internal (eg the library catalogue) resources

Blacklight**: an open source discovery solution. It does not include a central index of electronic resources

VuFind**: an open source discovery solution. It does not include a central index of electronic resources

LeanLibrary**: (Technology from Sage) a web browser extension that enables users to search using tools such a Google or an abstract and index database.A check is made to see if the resource is subscribed to by the library so enabling the user to avoid any potential paywall

LibKey Discovery**: a web browser extension that enables users to search using tools such a Google or an abstract and index database.A check is made to see if the resource is subscribed to by the library so enabling the user to avoid any potential paywall

EndNote Click**:(Clarivate) (was Kopernio). Brings subscriptions and open access content into researchers' workflows. A free browser plugin

UnPaywall**. A web browser extension. An open database of 49 million free scholarly articles.It harvests Open Access content from over 50,000 publishers and repositories. Unpaywall is often integrated into other discovery services and solutions

CORE Discovery** A web browser extension that has a preference for displaying first the open access content, originating from approved content providers (primarily open content repositories) , and seeks alternative routes, providing access to free versions, only if they are not available from them.

BASE**:provides more than 340 million documents from more than 11,000 content providers. Users can access the full texts of about 60% of the indexed documents for free (Open Access). BASE is operated by Bielefeld University Library.

Google Scholar**: Article-level links to subscription full text for patrons affiliated with a library is provided by Google 'Library links'. This works best for electronic resources, such as journal and conference articles. Needs an OpenURL compatible link resolver

Sci-Hubis a shadow library website or disputed legality that provides free access to millions of research papers, regardless of copyright by bypassing publishers' paywalls in various ways

A Very Small Pond: Discovery Systems That Can Be Used with FOLIO in Academic Libraries. By Aaron Neslin & Jaime Taylor. Code{4}lib Journal. August 2023.

As well as identifying discovery solutions that do (and mostly don't) work with the FOLIO open source library system the article provides a helpful summary of the different kinds of discovery solutions including:

• Single Search Discovery Layers
• OPAC-Like Front Ends – Open Source Options
• OPAC-Like Front Ends – Proprietary Options

Discovery services.Chapter 1. Introduction. By Marshall Breeding. ALA Techsource Vol 54, No 8 (2018)

“This issue of Library Technology Reports gives an updated look at the realm of discovery products implemented in libraries, focusing especially on how these products have been implemented in academic libraries. It is the third issue of Library Technology Reports produced by this author addressing topics related to library catalogs or discovery services”.

Discovery Services: Basics and Resources. James M Day. Library Technology Launchpap. March 2017
An introduction based on the Summon discovery service

Resource Discovery for the Twenty-First Century Library

Dempsey, Lorcan 2020. Foreword to Resource Discovery for the Twenty-First Century Library: Case Studies and Perspectives on the Role of IT in User Engagement and Empowerment, xxi–xxxii. Edited by Simon McLeish. London: Facet Publishing. OCLC Research Foreword Preprint. https://doi.org/ 10.25333/p8j4-1411.
Full Book citation
McLeish, Simon (ed.). 2020. Resource Discovery for the Twenty-First Century Library: Case Studies and Perspectives on the Role of IT in User Engagement and Empowerment. London: Facet Publishing

Library Discovery System: An integrated approach to resource discovery
Sonawane, Chetan S Library Discovery System: An integrated approach to resource discovery. Informatics Studies, 2017, vol. 4, n. 3, pp. 27-38. Provides an overview of discovery services including (central index based) commercial solutions, open source options. Includes discussion of Google Scholar and issues around metadata, APIs etc

How Readers Discover Content in Scholarly Publications** 2018 Report: by Renew publishing consultants

(How Readers Discover Content in Scholarly Publications. 2018. By Tracy Gardner and Simon Inger Published by Renew Publishing Consultants August 2018)

Renew Publishing Consultants published the findings to two major research projects. How Readers Discover Content in Scholarly Publications 2018 is the latest in a series of reports spanning 13 years identifying the trends in user discovery behaviour. The latest research was carried out with the support of leading publishers and intermediaries, and attracted responses from over 10,000 people working and studying across all sectors, subject disciplines and regions. Headline results include:

• SciHub is responsible for around 5% of downloads in the wealthier nations (and must pose a special threat since the content available there is normally the final published version).
• Around 60% of the time people are reading articles from a “free” resources (it is likely PMC is responsible for much of this in the medical sector).
• In the academic sector as a whole, abstracting and indexing databases (A&Is) still appear to be the most important starting point in search.
• Academic search engines (such as Google Scholar) are more important than general search engines.
• Library discovery seems to have peaked in its importance-rating and is only holding a strong position in Humanities, Education and Social Sciences.
• Whilst searching as a discovery method dominates, it still only accounts for around 45% of people’s behaviour. Around 55% of the time people found the article they needed via other methods, eg following links on social media, emails and alerts, browsing other resources.

The Future of Library Resource Discovery
A white paper commissioned by the NISO Discovery to Delivery (D2D) Topic Committee
By Marshall Breeding February 2015

“This paper provides an overview of the current resource discovery environment and discusses some of the possibilities regarding how these technologies, methodologies, and products might be able to adapt to changes in the evolving information landscape in scholarly communications and to take advantage of new technologies, metadata models, or linking environments to better accomplish the needs of libraries to provide access to resources”. NOTE a shorter summary version is available- The future of resource discovery . Marshall Breeding. Information standards quarterly. Spring 2015. Vol 27. Issue 1. ISSN 1041-0031

E-resource Knowledge Bases and Link Resolvers: An Assessment of the Current Products and Emerging Trends”. Breeding, Marshall. 2012. Insights 25 (2): 173–82. DOI: http://doi.org/10.1629/2048-7754.25.2.173Insights 25 (2): 173–82. DOI: http://doi.org/10.1629/2048-7754.25.2.173

“This article summarizes the findings of a study on e-resource knowledge bases and OpenURL-based link resolvers sponsored by the National Library of Sweden. The project involved soliciting detailed information from each of the providers of the major products in this genre, reviewing product information available on the web and in published articles, and conducting a survey addressed to libraries using these products. The report identified and presented comparative information on a top tier of products that includes KnowledgeWorks and 360 Link from Serials Solutions; SFX Global KnowledgeBase and the SFX link resolver from Ex Libris; LinkSource and the EBSCO Integrated Knowledge Base from EBSCO and the WorldCat knowledge base from OCLC. A second tier included TOUResolver from TDNet, Gold Rush from the Colorado Alliance of Research Libraries and GODOT from Simon Fraser University”.

Selecting link resolver and knowledge base software: Implications of interoperability, Cyndy Chisare, Jody Condit Fagan, David Gaines & Michael Trocchia (2017) Journal of Electronic Resources Librarianship, 29:2, 93-106, DOI: 10.1080/1941126X.2017.1304765

“Link resolver software and their associated knowledge bases are essential technologies for modern academic libraries. Because of the increasing number of possible integrations involving link resolver software and knowledge bases, however, a library's vendor relationships, product choices, and consortial arrangements may have the most dramatic effects on the user experience and back-end maintenance workloads. A project team at a large comprehensive university recently investigated link resolver products to increase efficiency of back-end workflows while maintaining or improving the patron experience. The methodology used for product comparison may be useful for other libraries”.

Discovery Comparison
By the Council of Chief Librarians Electronic Access & Resources Committee. (CCL­EAR ) Spring 2016

In Spring 2016, selected members of the Council of Chief Librarians, Electronic Access and Resources Committee (CCL­EAR) undertook a
comparative study of five discovery tools:
● Ebsco Discovery Service (EDS)
● Encore Synergy
● Primo
● Summon
● Worldcat Local and Discovery
The review focused on the coverage, search interface, cost, availability/accessibility of service, and customer service as well as customization, and mobile options for each product.During Fall 2015 and Spring 2016 CCL­EAR conducted a comparison review of Discovery Services for the California Community Colleges. To inform the comparison a survey was sent to the 113 colleges to learn if institutions were using Discovery Services, if so, what they were and what were their experiences with different aspects of the Discovery Services. If institutions did not have a Discovery Service they were asked why and if they were interested in having one. In February 2016 CCL­EAR hosted a Discovery Services meeting and panel where all 113 colleges were invited. The survey results were reported and a panel discussion followed. Open discussion after the panel revealed a number of concerns and CCL­EAR realized a comparison review would be challenging. Each interface was highly customizable. Content was based on the subscription databases the college had and the visibility and results ranking was based on the Discovery Service. Some products were integrated with Integrated Library Systems (ILS) and other were stand alone products.Reviewers were granted guest access to products across the state, CCL­EAR conducted this comparison review.Evaluating Web-Scale Discovery Services: A Step-by-Step Guide
Joseph Deodato Information Technology and Libraries. Vol 34, No 2 (2015)
Abstract
Selecting a web-scale discovery service is a large and important undertaking that involves a significant investment of time, staff, and resources. Finding the right match begins with a thorough and carefully planned evaluation process. In order to be successful, this process should be inclusive, goal-oriented, data-driven, user-centered, and transparent. The following article offers a step-by-step guide for developing a web-scale discovery evaluation plan rooted in these five key principles based on best practices synthesized from the literature as well as the author’s own experiences coordinating the evaluation process at Rutgers University. The goal is to offer academic libraries that are considering acquiring a web-scale discovery service a blueprint for planning a structured and comprehensive evaluation process.

Discovery services White paper.Texas State Library & Archives Commission (Revised edition August 2015)
“This paper attempts to provide an overview of discovery services, including their advantages, disadvantages, limitations and best practices. In addition, a synopsis of the major discovery vendors is provided in Appendix A”

NISO Open Discovery initiative

The Open Discovery Initiative (ODI) is

• A technical recommendation for data exchange including data formats, method of delivery, usage reporting, frequency of updates and rights of use
• A way for libraries to assess content providers’ participation in discovery services
• A model by which content providers work with discovery service vendors via fair and unbiased indexing and linking
• A way to disclose and assess open discovery conformance for content providers, discovery providers, and libraries

It 'aims at defining standards and/or best practices for the new generation of library discovery services that are based on indexed search. These discovery services are primarily based upon indexes derived from journals, ebooks and other electronic information of a scholarly nature. The content comes from a range of information providers and products–commercial, open access, institutional, etc.The group is establishing a more standard set of practices for the ways that content is represented in discovery services and for the interactions between the creators of these services and the information providers whose resources they represent.' The ODI working group was formed in late 2011 and held its first meeting in January 2012.