Standards Update

Linked Data: What Is It and What Can It Do?

Mark H. Needleman, Column Editor

Needleman is SFX/MetalGainesville, FL 32606, US

0098-7913/$ – see frontdoi:10.1016/j.serrev.201

There has been a lot of talk, discussion (andevenbuzz) on the Internet and in the libraryworld recentlyon the whole issue of linked data and what it may mean, accomplish, and even change in the Internetand library worlds. This article will attempt to clarify what linked data is, some of the issuessurrounding it, and explore some possible implications. Serials Review 2011; 37:234.© 2011 Elsevier Inc. All rights reserved.

Linked Data

In a paper entitled “Linked Data—The Story So Far,” linked data isdescribed as follows: “The term Linked Data refers to a set of bestpractices for publishing and connecting structured data on theWeb.”1 The paper also outlines the principles of linked data design:

• Use URI to indentify things;• Use HTTP URIs (uniform resource identifier) so that these thingscan be referred to and looked up (“dereferenced”) by people anduser agents;

• Provide useful information about the thing when its URI isdereferenced, using standard formats such as RDF/XML; and

• Include links to related URIs in the exposed data to improvediscovery of other related information on the Web.

To put it simply, linked data is about using the Web to createtyped links between data from different sources. Linked data refersto data published on the Web in such a way that it is machine-readable, its meaning is explicitly defined, it is linked to otherexternal datasets, and can in turn be linked to from externaldatasets. There are detailed technical issues underpinning linkeddata that are too involved to go over in the space allowed here.However, descriptions of the technologies involved in linked datacan be found in “Linked Data—The Story So Far.”

To examine linked data from a library perspective, it should benoted that most (if not all) modern online public access catalogs(OPAC) provide some aspect of linked data in that record displayscreate links from such fields as author, subject headings and manyothers that theuser can clickon.However the links (usually) are onlyto searches in the OPAC and not to external resources. With a linkeddata implementation those links would provide the ability to accessresources beyond what is available in the OPAC itself. In addition,the links tend to be uni-directional—outbound from the OPAC, butbasically to other data residing in the OPAC itself. A true linked dataenvironment would provide the ability for external resources toprovide inbound links to those fields in the OPAC record.

ib Support Specialist, Florida Center for Library Automation,A; e-mail: mneedlem@ufl.edu.

matter © 2011 Elsevier Inc. All rights reserved.1.06.005

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Many interesting issues surround linked data, some of whichare still research questions. Among them are:

• Link maintenance—The content of linked data sources, like otherURIs on the Web, can change. Keeping links valid is currently achallenge and will become more of one as the use of linked datagrows. Mechanisms will be needed that can automatically checkand update links. Suchmechanisms exist today, but the question ofwhether they will be robust enough or whether newmechanismswill be needed is very much an open question;

• Licensing—Inevitably some data accessed through linked datamechanisms will have license restrictions attached to it. How theuser interface will deal with data that are not accessible by aparticular user is an issue for user interfaces like Web browsers;

• Trust, quality, and relevance—A significant consideration for linkeddata application is how to ensure the data most relevant orappropriate to the user's needs are identified and made available.For example, in scenarios where data quality and trustworthinessare paramount, how can this be determined heuristically, partic-ularly where the data set may not have been encounteredpreviously?; and

• User interfaces and interface design—One of the key benefits oflinked data from the user perspective is the provision of integratedaccess to data from awide range of distributed and heterogeneousdata sources. Thismay involve integration of data from sources notexplicitly selected by theuser. Challenges remain inunderstandingthe user interaction paradigm for applications built on dataassembled dynamically in this fashion.

Whilemany, if not all, of these issues and changes exist in today'sWeb environment, the development of linked data and applicationsthat make use of it will increase these challenges in the future.

Notes

[1] Christian Bizer, Tom Heath and Tim Berners-Lee, “Linked Data—The Story SoFar,” http://eprints.ecs.soton.ac.uk/21285/1/bizer-heath-berners-lee-ijswis-linked-data.pdf (accessed May 22, 2011).

Resources

Berners-Lee, Tim. “Tim Berners-Lee on the NextWeb.” Presentation given at the 2009TED Conference. http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html(accessed May 22, 2011).Wikipedia, The Free Encyclopedia. “Linked Data.” http://en.wikipedia.org/wiki/Linked_Data (accessed May 22, 2011).