Int J Digit Libr (2014) 14:181–195DOI 10.1007/s00799-014-0116-0

Sustainability of digital libraries: a conceptual modeland a research framework

Gobinda Chowdhury

Received: 1 November 2013 / Revised: 9 May 2014 / Accepted: 14 May 2014 / Published online: 7 June 2014© Springer-Verlag Berlin Heidelberg 2014

Abstract This paper aims to develop a conceptual modeland a research framework for study of the economic, socialand environmental sustainability of digital libraries. Themajor factors that are related to the economic, social and envi-ronmental sustainability of digital libraries have been identi-fied. Relevant research in digital information systems and ser-vices in general, and digital libraries in particular, have beendiscussed to illustrate different issues and challenges associ-ated with each of the three forms of sustainability. Based onthe discussions of relevant research that have implicationson sustainability of information systems and services, thepaper proposes a conceptual model and a theoretical researchframework for study of the sustainability of digital libraries. Itshows that the sustainable business models to support digitallibraries should also support equitable access supported byspecific design and usability guidelines that facilitate easier,better and cheaper access; support the personal, institutionaland social culture of users; and at the same time conformwith the policy and regulatory frameworks of the respectiveregions, countries and institutions. It is also shown that mea-sures taken to improve the economic and social sustainabilityshould also support the environmental sustainability guide-lines, i.e. reduce the overall environmental impact of digitallibraries. It is argued that the various factors affecting thedifferent sustainability issues of digital libraries need to bestudied together to build digital libraries that are economi-cally, socially and environmentally sustainable.

Keywords Digital libraries · Sustainability · Socialsustainability · Economic sustainability · Environmentalsustainability

G. Chowdhury (B)Northumbria University, Newcastle, UKe-mail: gobinda.chowdhury@northumbria.ac.uk

1 Introduction

The word sustainability has gained much importance over thepast few years, and it is now discussed in almost every busi-ness and in every sphere of life. According to the US Environ-mental Protection Agency (EPA), sustainability “creates andmaintains the conditions under which humans and nature canexist in productive harmony that permit fulfilling the social,economic and other requirements of present and future gen-erations” [1]. There are three forms of sustainability viz. eco-nomic sustainability, social sustainability and environmentalsustainability. Although the overall aim of any business ordevelopment is to achieve sustainability in all its three forms,in reality it is a major challenge because often measures aretaken for achieving one form of sustainability influence oraffect the other forms of sustainability. This paper discussesall the three forms of sustainability in the context of digitallibraries. It identifies some factors that have impact on eachform of sustainability. Relevant current research reports andpapers are used, not to exhaustively review the developmentsin the specific fields per se but to illustrate various issues andchallenges for the economic and social sustainability of dig-ital libraries. Similarly the paper draws upon some currentresearch in green IT and cloud computing to illustrate someissues of environmental sustainability that are relevant fordigital libraries. Based on these discussions this paper pro-poses a conceptual model for sustainable digital libraries, andthus proposes a theoretical framework for study and researchin this area.

2 Sustainability of digital libraries

Sustainable information refers to resources that facilitateintegration of all the three parts of sustainable development

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viz. social, economic and environmental sustainability, andcontributes to the strengthening of the processes in whichsociety is transformed according to the ideals of sustainabledevelopment [2]. Overall, the concept of sustainability hasnot been researched well either within the mainstream infor-mation science in general or within the context of digitallibraries in particular [2,3].

A digital library is an evolving organization and comprisesthree distinct systems—viz. a Digital Library that providesdigital content to its users through a series of functionali-ties that are controlled by some quality and policy measures;a Digital Library System which is a software system thatsupports the functionalities of a Digital Library; and a Digi-tal Library Management System which is a generic softwaresystem that provides the appropriate infrastructure for thefunctionalities of the Digital Library System [4]. The DigitalLibrary Reference Model (DRLM) [4] identified three cate-gories of actors that are fundamental to the operation of theDigital Library service, viz.

1. the DL end-users: content creators and content con-sumers;

2. the DL managers: DL designers and DL system adminis-trators; and

3. the DL software developers.

To study all the three forms of sustainability of digi-tal libraries, it is necessary to identify the challenges thatare associated with all the three systems that form a digitallibrary, as discussed above, and also the activities and func-tions of all the actors. Furthermore, depending on the levelof details that one wants to achieve, a study of the sustain-ability of digital libraries may also consider factors influ-encing the lifecycle of information—content and data fromtheir creation to management, use/re-use, and disposal (whenrequired, for example disposal of analogue informationresources and also disposal of computing infrastructure andequipment used for creation, management, access and use ofdigital information) [5]. Although the DRLM [4] providesdifferent levels of abstraction that lead from the “modelingto the implementation” of digital libraries, it does not specif-ically show how the different actors, and the functions andactivities can support or influence the three different forms ofsustainability of digital libraries. This paper aims to addressthis issue by proposing a conceptual model and a researchframework for study of the sustainability of digital libraries.

Before developing a model and a framework for study ofthe sustainability, it is necessary to determine the target andvarious indicators, for each form of sustainability of digitallibraries. In the context of digital libraries,

• the target for economic sustainability is to provide cheaper,easier and better access to quality digital information

through a sustainable business model. The success canbe achieved by building a sustainable business model—‘for profit’ or ‘not-for-profit’ depending on the serviceprovider and their characteristics—as well as throughmeasures for reduction of cost in the process of creation,distribution and access to information; and also by tak-ing measures for reduction in the user time and efforts fordiscovery, access and use of information relevant to theirspecific needs, context, culture and work practices, etc.;

• the target for social sustainability is to ensure equitableaccess to information to build a better (well informed)and healthy society. The success can be achieved (a) byimproved accessibility and usability relevant to the usercontext, culture, etc., and (2) by building tools and tech-niques for measuring and improving the impact of digitallibraries in every sphere of life and society; and

• the target for environmental sustainability is to ensurereductions in the environmental impact of digital informa-tion systems and services. The success can be achievedby building appropriate tools and techniques as well asmeasures to reduce the greenhouse gas (GHG) emissionsthroughout the lifecycle of digital libraries.

Many of these factors are interrelated, and therefore can-not be considered in isolation. For example, the rapidlychanging ICT infrastructure and information design to dealwith digital content and data will have implications for allthe three forms of sustainability of digital libraries: (1) onthe economic sustainability because of the increasing costs,increasing levels of efforts or specific needs for the deploy-ment of high-end ICT equipment for management of, andaccess to, information, etc. (2) on the social sustainabilitybecause of changes in the level of equitable access, andeffects on the users’ work and culture, and perhaps causingmore social exclusion caused by the unequal, or even lackof, ICT and internet access, and (3) on the environmentalsustainability in terms of increase in the GHG emissions dueto quick changes in, and disposal of, the ICT equipment andinfrastructure, and so on. Furthermore there are a number ofexternal factors that form the foundations of digital libraries,such as the emerging ICT infrastructure and policies; the fastchanging web, social networking and mobile technologies;the emerging intellectual property rights (IPR), privacy andsecurity issues, and so on. Often these factors play a signifi-cant part in each area of sustainability and thus affecting theoverall sustainability of digital libraries.

Some past research have indirectly touched upon the dif-ferent forms of sustainability of digital information services.For example, a number of alternative business models fordigital information services have been studied in the contextof e-books and e-journal subscription models in libraries,and also in the context of open access models (see for exam-ple [6]). Similarly there have been many evaluation studies

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focusing on the impact of digital library services. A signif-icant amount of research has taken place in the broad areaof user studies as well as digital literacy, social inclusion,etc. in the context of digital libraries (for a review see [7]).Recently, Chowdhury [3,8–10] has discussed the environ-mental issues and challenges of digital information systemsand services. However, to date very little research has beenundertaken addressing all the three forms of sustainabilityin tandem to understand the different factors that influencethe sustainability of digital libraries, and their implicationsas well as their interrelationships in the context of the design,development and management of digital libraries [3].

3 Economic sustainability of digital libraries

As stated earlier in the paper, the target for the economicsustainability of digital libraries is to ensure cheaper, easierand better access to digital information through a sustainablebusiness/funding model. Thus for digital libraries, economicsustainability can be achieved by:

1. building a sustainable business model supporting the eco-nomic, technological and manpower resources for thedesign, delivery and management of digital content anddata to meet the present and future needs of the user com-munities and society, and

2. a sustainable model for providing the economic, techno-logical as well as intellectual support for preservation ofdigital content and data.

Although it has been talked about in several publications,the economic sustainability of digital libraries still remainsa challenge requiring further research and innovation [11].

3.1 Sustainable business models for digital libraries

While some digital libraries are based on commercial models,i.e. they require payment or subscriptions for access, manydigital libraries have appeared over the past two decades orso that are free at the point of use. Such digital libraries arefunded by:

1. governments, e.g. the US National Science Founda-tion providing support for the National Science DigitalLibrary, or the National Library of Medicine as part ofthe US National Institute of Health providing funds forPubMed;

2. specific countries/institutions or consortia for example,various EU countries providing support for Europeana,or specific institutional repositories; and

3. charities, e.g. the Wellcome Library funded by the Well-come Trust.

However, sustainable funding is still a major issue formany digital libraries. For example, it was reported that “thecommitted and received funding from 21 countries has meantthat Europeana has fully covered both project-matching andoperating costs through to the end of 2012. However for theyear 2013, Europeana needs to raise additional funds of e426,000” [12].

Very few of the earlier digital library evaluation studiesfocused primarily on the economic sustainability of digitallibraries [13]. It is generally agreed that measuring the impactof information services in general, and digital libraries in par-ticular, is difficult because it is not easy to convert the benefitsof information services to Dollar figures. However, of latesome studies have attempted to measure the impact of digitallibraries on the economy as a whole. For example, the Euro-peana case for funding document [14] points out that over thepast 5 years, initial EU investment of 150 million euros hasresulted in 70 million euros of co-funding from Ministriesin 21 countries. The document reports that these investmentshave facilitated massive digitization in different EU mem-ber countries and as a result over 30 million digital objectsare now available through Europeana. It is also reported thatas of 2013 “770 businesses, entrepreneurs, educational andcultural organisations are exploring ways of including Euro-peana information in their offerings (websites, apps, gamesetc.) through our API” [14]. The document also points outthat Europeana has helped in the creation of new jobs; forexample, it reports that in Hungary, “over 1,000 graduatesare now involved in digitizing heritage that will feed in toEuropeana. Historypin in the UK predicts it will double insize with the availability of more open digital cultural her-itage”. Such measures of the impact of digital libraries on thewider economy, job markets, etc. are essential, albeit oftenvery difficult and time consuming, for justifying the case forfunding, and thereby achieving the economic sustainabilityof digital libraries.

3.2 Open access and economic sustainability of digitallibraries

The Green route to OA, that is based on self-archiving ofresearch papers, has given rise to thousands of institutionalrepositories. For example, the OpenDOAR directory has over2,500 listings of institutional repositories. However, differentinstitutions follow different practices for the creation andmanagement of institutional repositories. A recent survey ofthe funding and deployment of institutional repositories [15]notes that:

• institutions that mediate submissions incur less expensethan institutions that allow self-archiving,

• institutions that offer additional services incur greaterannual operating costs than those who do not, and

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• institutions that use open source applications have lowerimplementation costs but have comparable annual operat-ing costs with institutions that use proprietary software.

Most research funding bodies such as the European Union,Wellcome Trust, Research Councils UK (RCUK), USNational funding bodies such as the National Institute ofHealth (NIH) have proposed their OA policies which willresult in the development of various open-access institutionalrepositories and digital libraries. However, it will be interest-ing to see how economically sustainable will these reposito-ries be under these newly introduced OA policies.

An earlier study commissioned by Jisc in the UK notesthat there are potential economic savings for universitiesfrom OA. It notes that if the universities in UK continue topay for journal subscriptions, as they do now, and also maketheir research output available through OA repositories, theamount of savings for universities, accrued from increasedefficiencies in the research and library handling processes,could range from £0.1 million to £1.32 million per annum[16]. However, it should be noted that there are costs asso-ciated with running the institutional repositories. The Jiscstudy further noted that [16]:

• Annual operating costs for the institutional repository,including the cost of depositing items, range from around£26,000 to almost £210,000; and

• The cost of depositing a single article varies from around£6.5 to £15.4, with the annual cost of depositing into therepository all articles produced by each university rangingfrom just over £4,000 to over £75,000.

It may be noted that the costs of institutional repositoriesvary quite significantly depending on the size and nature ofthe universities, their research income and activities, num-ber of research papers produced per year, and so on. Even ifone takes an average of these two extremes, i.e. an averageof £135,000 per annum for running an institutional repos-itory, the total costs for 166 Higher education institutionswould be £22.4 million per year which is nearly 15 % of theannual journal subscription budget of UK universities whichis estimated to be £150 million [17]. The overall costs formanaging institutional repositories would be much higherover the years especially when the digital preservation costsare included in this.

3.2.1 Economic sustainability of digital preservation

Economic sustainability has also remained a major chal-lenge within digital preservation research. Over the pastdecade digital preservation research has mainly focused onthe design, architecture and software solutions for manage-ment of digital collections and creation of various preserva-

tion tools [18]. Several attempts have been made to createa research agenda for digital preservation over the past fewyears. For example,

• in 2007, the Digital Preservation Europe (DP) project iden-tified 10 fields of research in digital preservation, viz.restoration, conservation, management, risk, significantproperties of digital objects, interoperability, automation,context, storage and experimentation; and

• a research seminar organized within the Dagstuhl seriesin 2012 addressed two major research questions viz. whatrole should the cloud play in preservation, and what stepsshould we be taking now to preserve the future of today’sdigital artefacts?

The EU DPimpact study demonstrated that “investing effortsand resources in securing future access to digital contentmakes a lot of sense in economic terms, as impacts—directand indirect—will be clearly positive and growing as the DP(digital preservation) market start to “Cross the Chasm” bypenetrating and developing the mainstream markets of theInformation Society” [19, p 103–104]. However, the studyalso noted that the memory institutions had ‘very limited’funding for preservation, as compared to ‘limited’ fundingin the scientific and research institutions; and for business,companies and enterprises, the funding for preservation isdone by project and is charged to overheads ([19, Table 2A,p. 34]. According to the Blue Ribbon Task Force report [20],economically sustainable digital preservation requires:

• a recognition of the benefits of preservation on the part ofkey decision-makers;

• incentives for decision-makers to act in the public interest;• a process for selecting digital materials for long-term

retention;• mechanisms to secure an ongoing, efficient allocation of

resources to digital• preservation activities; and• appropriate organization and governance of digital preser-

vation activities.

The Blue Ribbon Task Force (BRTF) final report recom-mends that “sustainable digital preservation requires a com-pelling value proposition, incentives to act, and well-definedroles and responsibilities. Digital preservation is a challengefor all of society because we all benefit from reliable, authen-tic information now and into the future” [20, p. 5]. It con-cludes that sustainable preservation is a societal concern andtranscends the boundaries of any content domain, and there-fore all parts of society—national and international agencies,funders and sponsors of data creation, stakeholder organiza-tions, and individuals—have roles in achieving sustainabil-ity. The economic sustainability reference model for digital

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assets [21] divides the economic sustainability challengesinto four major components, viz.

1. the economic lifecycle, i.e. the background against whicha digital curation activity operates;

2. the sustainability strategy which should ensure that thecuration activities meet BRTF’s five necessary conditionsfor economic sustainability, viz. value, selection, incen-tives, resources, and organization/governance;

3. economic risks and remedies, i.e. the potential obstacles toachieving economic sustainability the potential solutionsfor mitigating or overcoming those; and

4. key entities, i.e. the digital assets, the curation process,and stakeholders.

Recognizing the lack of a continuous source of fund-ing for digital preservation, an EU FP7 research project,called SHAMAN, proposed an enterprise architecture-basedapproach that enables the accommodation of digital preser-vation concerns in the overall architecture of an organiza-tion with the justification that although the preservation ofcontents is not a main business requirement, it is requiredto enable actual delivery of value in the primary business[22]. Although this may resolve some problems of preser-vation of digital records within an institution, this does notspecifically resolve the issues that digital libraries and infor-mation services, for example institutional repositories, facefor preservation of digital data and content to ensure futureaccess.

Increasingly library and information services are mov-ing towards a shared or consortia-based approach for digitalpreservation. The HathiTrust digital library brings togetherhuge collections of partner institutions in digital form, pre-serving them securely for current and future access. In arecent move, seven European countries are launching the4C (the Collaboration to Clarify the Costs of Curation)to help public and private European organizations investmore effectively in digital curation and preservation, sus-taining the long-term value of all types of digital informa-tion [23]. The 4C partners involved are Danish NationalArchives (Denmark), DANS—Data Archiving and NetworkService (Netherlands), Deutsche Nationalbibliothek (Ger-many), Digital Curation Centre (UK), Digital Preserva-tion Coalition (UK), Humanities Advanced Technology andInformation Institute (UK), Institute for Information Systemsand Computing Research (Portugal), Jisc (UK), Keep Solu-tions (Portugal), National Library of Estonia (Estonia), RoyalLibrary of Denmark (Denmark), Secure Business (Austria),UK Data Archive (UK). It is widely recognized that thecosts of curation are currently hard to predict and secondlythe short-term benefits are hard to define because curationimplicitly addresses long-term challenges. It is reported that4C will address both concerns and provide practical guidance

that will help practitioners persuade executives to invest innew services [23].

3.3 Challenges

The major challenge for the economic sustainability of digi-tal libraries arises from the very nature and purpose of digi-tal libraries. Measuring the economic sustainability of a ser-vice sector, i.e. the tangible returns or measuring the valuefor money of a digital library service, is a major challenge,because often digital libraries do not make direct profits ortangible assets. Digital libraries produce “intangible” goods,such as development and progress in government, health,education, etc., and the overall society and the knowledgeeconomy. The WorldBank Group report [24] proposes thatone of the indirect measures for the economic sustainabilityof service sectors can be the growth in the human capitalthat is capable of engaging in sustainable development usingfewer natural resources, alternative and innovative technolo-gies and resources, and so on. Therefore, one should use suchindirect measures or indicators for the economic sustainabil-ity of digital libraries. However, measuring the volume andvalue of such intangible goods is not only a challenging task,but may also take a long time to measure the impacts, e.g.the impact of a good digital library service on education andresearch, health, and so on. Although some indirect mea-sures have been proposed, for example, as in the Europeanacase for funding document, discussed earlier, certainly moreresearch is needed to identify and develop different mea-surable indicators for the economic sustainability of digitallibraries.

4 Social sustainability of digital libraries

Social sustainability may be defined as the maintenance andimprovement of well-being of the current and future genera-tions of people [25]. However, the concept of well-being canbe defined differently in different contexts ranging from theequity of access to essential services for healthy lifestyle andwell-being, to democratic and informed citizenship, to pro-motion and sharing of positive relations and culture, and soon. Many indicators of sustainable development have beenproposed (see for example, [26,27]), but broadly speakingthe main goal of the social sustainability of digital librariesis to ensure equitable access and ease of the use of digitalinformation in every sphere of life and society.

Ideally speaking a socially sustainable digital library orinformation service should be ubiquitous, i.e. it should beembedded in the work and culture of people in such a waythat they get access to the information that is relevant to theirwork or activities even without having to actively ask forit. Access is a rather broad term here that includes all theactivities related to the discovery, access and use/re-use of

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information for day-to-day business, pleasure, well-being,knowledge and understanding, and so on.

A number of parameters are associated with the socialsustainability of digital libraries that have direct or indirectinfluence on equitable access, such as:

1. HIB (human information behaviour) and IS&R (informa-tion seeking and retrieval) issues;

2. Information and digital literacy issues;3. Accessibility and usability issues including access to the

ICT and internet facilities, digital library software andinterface issues; and

4. Policy and legal issues.

4.1 Social sustainability and digital library

A number of models for digital libraries such as the 5S model(Streams, Structures, Spaces, Scenarios and Societies [28])and the DRLM [4], and a number of software platforms suchas DSpace, EPrints, Fedora Commons, Greenstone, etc., haveappeared over the past two decades. Similarly a variety oftools, metadata standards and protocols for metadata harvest-ing, such as the OAI-PMH [29], have also been developedover the past few years. These digital library architectures,software, tools and standards aim to facilitate better and eas-ier access to information, and thus improve the social sus-tainability of digital libraries.

The DRLM is built on six main domains, viz. content, user,functionality, quality, policy and architecture [30]. Accordingto this model, the three systems, viz. the Digital Library, Dig-ital Library System, and Digital Library Management Systeminteract with the six domains to provide digital library ser-vices. The 5S model describes how various components ofdigital libraries interact or relate to each other. For example,digital objects are composed of Streams (bit streams) andStructures (e.g. structural metadata specification), that can beaccessed through Spaces (e.g. indexing) through some Sce-narios (e.g. sequences of events or actions such as searching,browsing, etc.) created by, or designed for, some Societies(e.g. user communities). Thus both the models recognize thatdigital libraries deal with digital objects that need to be man-aged and processed for providing access to the user commu-nity through a series of functions. DRLM also emphasizeson the quality of the content and services, and the policyissues. Therefore, these models implicitly argue in favour ofthe social sustainability of digital libraries which dependson a series of functions and policies for better organization,indexing, linking and retrieval of digital information that areappropriate for the context, culture and practices of the usercommunity and society. Usability of digital libraries is oftenaffected by the user needs and expectations that are set, oftenvery rapidly, by the recent developments in the internet andweb technologies, especially the popular search engines and

digital information services. However, as discussed later inthe paper (in Sect. 7), these models do not make provisionsfor explicitly addressing the challenges associated with allthe three forms of sustainability. This is discussed in moredetails in Sect. 7.

4.2 HIB and IS&R issues

HIB and IS&R have remained the two most widely researchedareas of information science for the past few decades giv-ing rise to several models in information science in gen-eral (for details see [31–33]) and in the context of digitallibraries in particular [34,35]. These models discuss variouspersonal, contextual, social, cultural and technological issuesthat influence access to, and use of, digital libraries.

As discussed in the previous section, open access hasbecome a major agenda amongst governments and researchfunding bodies. However, still there are some major cul-tural issues that need to be addressed to make it a success.For example, one may argue that the Finch Report [17] andRCUK OA policies based on the APCs (article processingcharges; discussed in Sect. 4.5), may create a situation wherepublication of a research paper may be decided not only byits quality but also by the affordability of the authors andinstitutions to pay the APCs of a target journal. Further-more, national research assessment exercises, like the UKresearch excellence framework (REF), Australian excellenceof research in Australia (ERA), and more importantly aca-demic and research appointments and promotions are stillvery much driven by the assessment of quality of researchin journals and conferences with high impact factors. Theseassessment measures may affect the social sustainability ofopen systems.

4.3 Information and digital literacy issues

Like human information behaviour, information literacy hasalso remained a major area of research in information studies.There are other related areas of research like digital literacy,digital divide, social inclusion, etc. Access to, and effectiveuse of, digital libraries can be significantly affected by poorinformation and digital literacy of people [7]. A November2012 BBC news [36] reports that 16 million people in Britain,i.e. about one in four, or one in three in the adult British pop-ulation, do not have the basic Internet skills. It may be safelyassumed that this is not an isolated case and many countries inthe world have comparable, or even worse, information anddigital literacy skills causing social exclusion. In the con-text of digital libraries, social exclusion may be caused by anumber of factors ranging from the lack of adequate accessto ICT infrastructure and services, to the lack of digital andinformation skills that are the pre-requisites for successfulaccess to, and use of, digital library services.

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4.4 Accessibility and usability issues

Access to, and effective use of, digital libraries can be sig-nificantly affected by digital divide that is often manifestedby [37]:

• the social divide which is characterized by the differencein access between diverse social groups;

• the global divide which is characterized by the differencein terms of access to the Internet technologies; and

• the democratic divide which is characterized by the differ-ent applications and uses of digital information to engageand participate in social life.

Different indicators may be used for assessing the differ-ent manifestations of digital divide [37]. Furthermore, digitaldivide is not only prevalent in the developing world, but alsoamongst various communities within the developed nations.For example, about a third of the US households do not havea broadband connection, and only about two-thirds of the 27EU countries have a broadband connection at home [37]. So,the vision of the Europeana digital library to provide digi-tal information and culture to everyone in Europe cannot befully utilized because two-thirds of the EU homes do not yethave a broadband connection. The situation in the third worldcountries is even worse.

Usability of digital libraries is often affected by the userneeds and expectations that are set, often wrongly, by thesearch engines. In a usability study of the Europeana digitallibrary it was noted that young users’ information needs andsearch strategies and expectations were quite different fromthose of more matured users [38]. The study further notedthat many younger users wanted to be able to download,annotate and share digital objects. The latter is a relativelynew phenomenon which is caused by the recent proliferationof the easy-to-use search engine services that have created adifferent set of expectations, especially amongst the youngerusers.

4.5 Policy and legal issues

Design and management of digital libraries are influencedby several policy issues. For example, the recent policies ofvarious research funding bodies with regard to open accesscan have a significant impact on the economic and social sus-tainability of digital libraries. Research and funding bodiesand institutions in many countries now support the motto ofopen access and encourage researchers to self-archive theirpublished research papers, some even make it compulsory.For example, the public access policy of the US NationalInstitute of Health (NIH) states that:

“all investigators funded by the NIH submit or havesubmitted for them to the National Library of Medicine’s

PubMed Central an electronic version of their final, peer-reviewed manuscripts upon acceptance for publication, to bemade publicly available no later than 12 months after theofficial date of publication.” [39]

The Wellcome Trust have also introduced a similar open-access policy that:

“requires electronic copies of any research papers thathave been accepted for publication in a peer-reviewed jour-nal, and are supported in whole or in part by WellcomeTrust funding, to be made available through PubMed Cen-tral (PMC) and Europe PubMed Central (Europe PMC) assoon as possible and in any event within six months ofthe journal publisher’s official date of final publication”[40]

The newly introduced OA policy of the European Com-mission [41] stipulates that as of 2014, all research papersproduced with funding from EU Horizon 2020 will haveto be freely accessible to the public. The process of self-archiving has given rise to several specialized digital librarieslike PubMed Central, and has given rise to institutional repos-itories at many specific institutional levels.

The Gold OA model has been adopted by many jour-nals whereby they have introduced article processing charges(APCs), and there are now some hybrid journals that followboth the subscription and APC-based open-access model.Some funding bodies have introduced inclusion of APCswithin their research funding models. For example, the OApolicy of the Wellcome Trust states that the Trust, whereappropriate, will provide their research grant holders withadditional funding, through their institutions, to cover open-access charges. The European Commission recommends thefollowing two options for OA [41]:

• Gold OA where research papers will be made immediatelyaccessible online by the publisher and the researchers willbe eligible for reimbursement of the APCs from the Com-mission; or

• Green OA where researchers will make their researchpapers available through an open-access repository nolater than six months after publication (or 12 months forarticles in the fields of social sciences and humanities).

A number of social, institutional and cultural issues areinvolved here. For example, it is not clear how the APC modelof Gold OA will be implemented, and similarly how the self-archiving of research papers will be adopted by the acad-emics and researchers across all the education and researchinstitutions and disciplines.

Access to, and use of, digital information is often hin-dered by the inappropriate, and often stringent, intellectualproperty rights (IPR) and complex digital rights management(DRM) issues. This has been identified in several studies(see for example, [42–44]). Considering the various recom-

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mendations of the Hargreaves Review [44], the UK Govern-ment commissioned a feasibility study that recommendedthe development of a Copyright Hub to serve a number offunctions including [45]:

• Information and copyright education;• Registries of rights;• A marketplace for rights-licensing solutions; and• Help with the orphan works problem.

The report concluded that a number of issues existed withcopyright licensing making them unfit for the digital age [45].However, it will be interesting to see how the new IP lawsinfluence the publishing industry and digital libraries.

5 Environmental sustainability of digital libraries

Digital libraries are based on a variety of ICT infrastruc-tures that run various information systems and services andthe overall lifecycle of a digital library. ICT has a profoundimpact on the environment causing about 2 % of global green-house gas (GHG) emissions [9,10]. GHGs comprise car-bon dioxide (CO2), methane (CH4), nitrous oxide (N2O),hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) andsulphurhexafluoride (SF6), but it is generally expressedthrough a common metric of CO2-equivalent emission[46].

The information services sector, by virtue of makingextensive use of ICT infrastructure and equipment, generatesa significant amount of GHG emissions. In 2010 Google’soverall consumption of electricity was reported to be 2.26million MWh [47]. This is equivalent to the annual emis-sions from about 11 power stations in Britain [9]. Anotherestimate shows that about one billion Google search is con-ducted every day, and thus even on a conservative estimate,one billion grams or 1,000 tonnes of CO2 (carbon dioxide,a measure used to show GHG emissions) is emitted onlyfor Google search every day [48]. This does not include theclient-side ICT and energy usage figures. It is estimated thatthe Internet consumes between 170 and 307 GW (GigaWatt)of electricity which is equivalent to 1.1–1.9 % of the totalenergy usage of humanity [49]. The HE institutions (HEIs)in the US produce 121 million tonnes of CO2 in a year whichis equivalent to nearly 2 % of total annual GHG emissionsin the US, or about a quarter of the entire State of Califor-nia’s annual emissions [50]. It is estimated that in 2008–2009, HEIs in the UK alone used nearly 1,470,000 comput-ers, 250,000 printers and 240,000 servers; and it is estimatedthat there would be 500,000 tonnes of CO2 emissions fromthis electricity use [51].

Some data related to the environmental impact of infor-mation services based on print and digital content are pro-

vided by Chowdhury [10]. Studies also show that use ofmodern technologies like cloud computing can reduce boththe economic and environmental impacts of digital informa-tion [3]. In the UK, Jisc is promoting the idea of using thecloud computing technology for providing data and infor-mation access services for the HEIs that can reduce theenvironmental costs of information services and the ICTinfrastructure costs. Some US universities are also takingsimilar initiatives in developing cloud-based systems formanaging research data and information [50]. In The Nether-lands, SURFnet is also taking several measures to pro-mote the use of cloud computing for higher education andresearch.

Thus, cloud-based information services can improve theenvironmental sustainability of digital libraries and informa-tion services [3,9]. However, a number of social-, cultural-and user-related issues are also associated with cloud-basedinformation services, e.g., access and management issuesrelated to sensitive data and content, information behaviourof users in relation to remote access to data and content; insti-tutional and user culture and practices in relation to accessand use of remote digital content and data, and so on. Todate no research has addressed all of these issues in tandemin relation to digital libraries, and specific user communitiesand contexts.

6 A research framework for sustainable digital libraries

Figure 1 presents a generic model and a theoretical researchframework for study of the sustainability of digital libraries.At the core, it shows that a digital library connects users withdigital content and data using the appropriate ICT. It alsoshows that while a sustainable digital library needs sustain-able funding models, appropriate measures should also betaken to achieve the social and environmental sustainabil-ity of digital libraries. The issues of sustainability should beconsidered in the context of the major factors influencingthe lifecycle of information—from creation to the manage-ment, use/re-use, and disposal, when required, of informationresource or tools and equipment, for example disposal of ana-logue information resources and also disposal of computinginfrastructure and equipment, etc.

The conceptual model and the research framework serveto illustrate that a number of factors are responsible for, andcontribute to, the different forms of sustainability of digitallibraries. These factors may be related to the digital contentand data, discipline and domain, user information behaviour,society and culture, ICT infrastructure, information design,legal and policy frameworks, and so on. Overall, the sustain-ability model can be used in association with various otherinformation models to study the issues and challenges asso-ciated with the sustainability of digital libraries.

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Sustainability of digital libraries 189

Fig. 1 A conceptual model anda research framework forsustainability of digital libraries

Economic SustainabilitySustainable DL Funding models

New Business models & Frameworks, e.g. OA models

Digital economyNew metrics for impact

assessment (value for money)

Environmental sustainabilityNovel cloud-based design &

architecture for DLs: Linked content and linked data

Sustainable digital preservation models

Toolkit for measuring environmental impact of DLs

Green IT/IS and Green user behaviour research

Social sustainabilityMeasures for equitable

access: User- & Context-specific design & usability

Information and digital skillsImproved web accessibility

Device independent accessChanges in culture: work,

institutional & personalSupporting policies & legal

frameworks

Sustainable Digital Libraries

Data &

Content

ICTUser

6.1 Influence of the research issues on different forms ofsustainability

It may be noted that the various research issues related to oneaspect of sustainability of digital libraries can have influence,positively or negatively, on the other forms of sustainability.As shown in Fig. 1, new funding and business models areneeded for achieving the economic sustainability of digitallibraries (see Sect. 7 for further discussions). However, suchmodels should also support the social and environmental sus-tainability. If measured in simple economic terms, buildinga sustainable business model, especially in the business con-text, i.e. for-profit digital library services, does not neces-sarily aim to achieve the social sustainability goal of freeand equitable access. Similarly, digital libraries may needto invest more resources to improve their design and usabil-ity if user- and context-specific digital library services areplanned for everyone. As opposed to the commercial models,not-for-profit business models should aim to develop alter-native metrics for measuring the impact and success of adigital library. Such measures may include contributions ofthe digital libraries in the overall sustainable development ofa society in terms of development of a better workforce, aknowledge economy, a healthy society, etc. However, as dis-cussed before, while such new business models and metrics

can promote both the economic and social sustainability ofdigital libraries, these cannot be achieved unless appropriatelegal and policy frameworks are developed to support suchactivities.

Green IT research shows that by adopting appropriatecloud computing technologies, digital libraries and informa-tion services can be more economically sustainable becauseof the economic and environmental benefits that such tech-nologies can offer [3]. However, such economic and environ-mental benefits may have some adverse effects on the socialsustainability of digital libraries unless appropriate legal poli-cies and guidelines are developed that are suitable for spe-cific business sectors. Similarly building of sustainable digi-tal preservation models will promote the social sustainabilityof digital libraries because it will ensure equitable access toknowledge for the present and the future generations. How-ever, building a sustainable digital preservation model needsmore and long-term investment, and such investment shouldgo hand in hand with the changing user needs and contexts—an area of HIB research according to the model in Fig. 1—the changing ICT infrastructure and technologies which is anarea of research for the environmental sustainability, and soon. Thus overall, this model can help us better understand thevarious research issues related to the different aspects of thesustainability of digital libraries and their influence on each

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Fig. 2 A conceptual model forstudy of the sustainability ofscholarly digital libraries

other. This is illustrated in the following section with exam-ples drawn from a scenario of digital libraries of scholarlyinformation.

7 Sustainability of digital libraries of scholarlyinformation

This section discusses how the proposed conceptual modelcan be used to understand and study the ways in which var-ious sustainability factors are related to, or influence, eachother, and thus how the measures taken for achieving oneform of sustainability can influence the other forms of sus-tainability. While Fig. 1 provides a generic model showingvarious research issues surrounding different forms of sus-tainability of digital libraries and information services, Fig. 2shows a model representing different actors and their inter-actions towards the overall sustainability of digital librariesin the context of open access and digital libraries of scholarlyinformation.

Figure 2 shows that there are eight major actors of a sus-tainable scholarly digital library model. Some of these actorsare People or Institutions and thus are similar to those iden-tified in the DLRM, but some like ICT & Infrastructure andKnowledge & Skills are more abstract, but they all have amajor role in the overall sustainability of digital libraries:

1. People: Creators & Consumers: The creators and con-sumers of information are the actors. They belong to asociety and are managed by the regulations, policies andpractices of one or more government, institutions andcommunities of practice. They may belong to a specificinstitution ruled by a government and/or a regulatory bodyand its various policies.

2. Institutions & Resources: These are the actors as wellas facilitators. Content creators and users belong to aninstitution, and in this regard they are the actors. Again

resources for content creation, in terms of staff salary,research funding, etc., are provided through institutionsand thus they are the facilitators. They also provide fund-ing and management support for digital libraries that areused by their people (information users).

3. Information Industry & Businesses: Traditionally theinformation industry comprised the conventional pub-lishers, distributors, online databases, aggregators, etc.However, in today’s world a number of new playershave entered the digital library and information mar-ketplace such as various OA repositories and digitallibraries, search engines and various specialized serviceslike Google Books, Google Scholar, Microsoft AcademicSearch, etc., that facilitate access to information. Overall,they support and facilitate the various information cre-ation as well as access processes.

4. Knowledge & Skills: These are the facilitators or keyenablers. Disciplinary knowledge and appropriate skills—information skills, digital skills, writing & communica-tions skills, etc., are essential for both the creation anduse of information and data. They are also the intangibleoutcome of digital library services.

5. Information: Content and Data: These are the products ofvarious activities performed by people in course of theirresearch and scholarly activities, as well as various day-to-day activities of the businesses that they are engagedin. In the context of digital libraries these are the schol-arly output (books, journal and conference papers, theses,reports, etc.) and datasets.

6. Information Systems & Services: These are designed andmanaged by people that belong to different institutions,and more often, in the information industry. In case ofdigital libraries these can be open-source or proprietarysoftware systems. They facilitate access to, and use of,Information: Content & Data.

7. ICT & Infrastructure: They are the key enablers. Theyform the backbone of all digital library activities and

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functions that are related to the creation as well as useof information—content and data. They are also the keyenablers for digital library access and use.

8. Society, Government & Regulatory Bodies: The entireinformation industry and the service sector, and their var-ious activities are governed, directly or indirectly, by avariety of government as well as international, regionaland national bodies that formulate the necessary policies,funding mechanisms, standards, guidelines, etc.

It may be noted that some of the components and therelated activities and functions are quite similar to theactors and functions identified by the previously devel-oped digital library models like the 5S and the DLRM.However, these models do not explicitly address, andshow the relationship among, the various sustainabilityissues.

The model in Fig. 2 shows that sustainable digital librariesreside at the intersection of the interactions amongst the dif-ferent actors. In other words, sustainability of digital librariescan be achieved as long as we can maintain a balance amongstall the different actors and their underlying forces. Some ofthe actors perform specific functions or activities, while theothers are the agents or facilitators for various activities, andsome are the outcome of different actions. In some cases,actors may be the beneficiaries, for example, People and Insti-tutions can be the creators as well as consumers of informa-tion. Some of the actors are facilitators as well. For example,Governments, Information Industries and Institutions are theactors because the information creators are part of them, butthey are also the facilitators because they formulate variousregulations, guidelines, standards and practices that controlthe processes of information creation as well as access anduse.

The model shown in Fig. 2 can be used to demonstrate thevarious processes of creation, access and use of informationin scholarly digital libraries. It can also be used to study thevarious factors that are responsible for the sustainability ofdigital libraries. Each vertex is linked to various other ver-tices based on the various activities involved in the creation,management and use of information. For example, the ver-tex People: Creators & Consumers and its linked verticesdemonstrate that:

• People create information (content and data) using appro-priate disciplinary and domain knowledge and skills (linksamongst the People—Information: Content & Data—Knowledge& Skills vertices);

• The information creation process takes place by the peopleand the information industry (links amongst the People—Information: Content & Data—Information Industry &Businesses vertices);

• The information creation process requires resources (linksamongst the People—Information: Content & Data—Institutions & Resources vertices);

• The information creation process is governed and facili-tated by specific government or regulatory bodies (includ-ing national/regional/international bodies) (links amongstthe People—Information: Content & Data—Society, Gov-ernment & Regulatory Bodies vertices);

• The information creation process is facilitated by theICT and infrastructure (links amongst the People—Information: Content & Data—ICT & Infrastructure ver-tices); and

• Access to information takes place through the specificinformation systems and services (links amongst thePeople—Information: Content & Data—Information Sys-tems & Services vertices).

Similarly, the vertex Information Systems & Services islinked with various other vertices and it demonstrates that:

• People use information systems and services to accesscontent and data (People—Information Systems & Ser-vices – Information: Content & Data vertices);

• People and the information industry and businesses worktogether to create, and sometimes manage, informationsystems and services (People – Information Systems &Services – Information Industry & Businesses vertices);

• People and specific institutions may create some informa-tion systems and services, e.g. institutional repositories(People —Information Systems & Services—Institutions& Resources vertices);

• People create information systems and services thatare governed or influenced by specific regulations, forexample the open-access regulations and policies ofvarious funding bodies that have given rise to manyinstitutional repositories (People—Information Systems& Services—Society, Government & Regulatory Bodiesvertices);

• People create information systems and services thatare facilitated by the available ICT and infrastructure(People—Information Systems & Services—ICT &Infrastructure vertices); and

• People use specific knowledge and skills to build and useappropriate information systems and services (People—Information Systems & Services—Knowledge & Skillsvertices).

7.1 A sustainability model for OA digital libraries

For the purpose of illustrating how the model shown in Fig. 2can be used, let us consider the recently introduced OA poli-cies of various funding agencies, as discussed earlier in the

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paper, and their implications for digital libraries of scholarlyinformation. According to the model proposed in Fig. 1, theOA policies can be considered as the new funding policies tosupport OA publishing directed towards the economic sus-tainability of scholarly digital libraries. However, not everyOA policymaker with the exception of some in the US, forexample, the National Institute of Health, and the WhiteHouse Office of Science and Technology Policy (OSTP)makes provision for the development and management ofOA services like building repositories or digital libraries ofOA content and data. In other words, costs for building andmanaging digital libraries of OA content and data are takenfor granted by many OA policy makers.

Furthermore, the impact of these OA funding policies onvarious actors needs to be studied. For example, the OA fund-ing policies will have a significant impact on (1) the contentcreators, i.e. researchers who publish research papers basedon whether they can afford to pay APCs or their accessibil-ity to research information because there will be a time lagdepending on whether a research is published through theGold or Green OA policy; (2) the publishing industry andjournals, etc. because there will be a different set of rulesbased on whether or not authors are charged, and when andhow the content is made available in the public domain; (3)the information service providers because universities andresearch councils may have to spend more money to buildand manage OA services; (4) web search engines may beable to offer better and more values-added services (e.g. withcitation data and linked research content and research data)when more and more research content and data are madeavailable in the public domain; (5) the content users becauseof the specific OA policies chosen by the content creators(Green or the Gold route to OA), the mechanisms put inplace for getting access to scholarly information—through aone-window search system or through specific institutionalrepositories, the corresponding embargo period imposed byvarious publishers, and so on. Furthermore, for this fundingto be sustainable, some measures of the success or impact ofdigital library services have also to be developed. These canonly be indirect measures, as discussed in Sect. 3, such as thecontribution of the digital library in the creation of knowl-edge and skills. Different methods and techniques have to bedeveloped for such indirect measures, and moreover these,being a long-time impact, can be assessed only after a rea-sonable period of time since the beginning of a digital libraryservice.

As discussed earlier in this section, the model in Fig. 2can help us understand this by looking at the various ver-tices and their links. Each of the vertices in Fig. 2 will havesome kind of relationship with, or fore on, one another;and a sustainable digital library can be built only when anequilibrium is reached. For example, some kind of relation-ship or force exists between the Information Industry and

the Government, Institutions, Information creators, Infor-mation (Content), and Information Systems & Services. Tobuild sustainable digital libraries the new OA policies shouldredefine or counteract these forces amongst the differentactors. Research shows that increasingly digital library usersare using mobile devices for accessing information, and alarge proportion of these accesses are search engine referrals[52,53]. From the sustainability of view, while platform- anddevice-independent access to digital information is ideal, thiswill have implications for the overall design of the digitallibraries. Again, appropriate arguments for sustainable fund-ing and better design and development of digital libraries canonly be justified when appropriate evidences can be gatheredthrough research as to how the digital libraries have, and canin future, improve the work and culture of people, businessesand society.

The OA policies will help us achieve the social sustain-ability of digital libraries because it will facilitate free accessto scholarly information. However, this does not guaranteeeasy or equitable access to digital information. There may beseveral stumbling blocks for achieving this. One of the expec-tations of the research funding bodies is that output from thepublicly funded research should be accessible to everyonein society. So, the obvious question is: how can we designdigital libraries of different types of content and data that cansupport better and easier access to information for everyonein society? Furthermore, as more and more research contentand data become available in the public domain, there willbe needs for long-term preservation of content and data thatwill require more resources, and will be more technologi-cally demanding—both in terms of disk space and appropri-ate tools and technologies. Thus, the OA policies should notonly provide resources for alternative modes of publishingcontent, but also provide support for building and managingthe appropriate information systems and services, and sup-port the institutions and individuals (information creators)by providing appropriate ICT and infrastructure and otherresources.

As more and more content and data become available inthe public domain, appropriate measures have to be taken tobuild environmentally sustainable digital libraries and preser-vation systems. The model in Fig. 2 can help us explain this.Over the past few years environmental issues have taken amajor place in business and policymaking in every govern-ment, industry and institution. The OA digital libraries willmake more demands for ICT energy, and hence we need tobuild various techniques and tools for measuring the envi-ronmental impact of digital libraries. Some environmentalsustainability measures may come from the use of energy-efficient hardware, software and network infrastructure, buta large part of it will come from the end-user ICT and infor-mation behaviour vis-à-vis the efficiency of the design ofspecific digital libraries. For example, the less time and more

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energy-efficient device (thin client) that a user can use toaccess and use information from a digital library, the moreenergy efficient, and thus more environmentally sustainablewill be the digital library. Thus, a variety of related researchissues need to be studied to build green information services,and the proposed model can guide us to identify and focus onsuch research issues. According to the model in Fig. 2, it willbe in the interests of the Government, Institutions and indi-vidual users (People) to use appropriate ICT to build moreenergy-efficient and therefore green Information Systems andServices. Research shows that cloud computing technologieshave some promises for the economic and environmentalsavings [3,9], but more research is required to build cloudarchitecture for digital libraries and digital preservation sys-tems that not only provide better and easier access, but alsoprovide adequate protection for various privacy and securityissues, an area of concern for several actors in Fig. 2, suchas People, Institutions, Information Industry & Business andGovernment.

8 Conclusion

To build sustainable digital libraries, attention should be paidto all the three areas viz. economic, social and environmentalsustainability. The conceptual model presented in this papershows that a number of stakeholders and factors are involvedin today’s world of digital libraries. The proposed model canbe used in conjunction with other digital library models. Forexample, the proposed model can be used in conjunctionwith the different functionality domain concept maps of theDRLM to study how a specific functionality of an actor—anend-user or a digital library manager, or a specific action,for example management and preservation of an informationobject, can influence—positively or negatively, the differentforms of sustainability. The economic sustainability refer-ence model, discussed in Sect. 3.2, shows that the economicsustainability challenges of digital preservation should beconsidered in the context of the overall economic environ-ment within which the preservation activities take place, aswell as the specific strategies for digital preservation, and therisks and benefits in the context of the concerned content andvarious actors. Overall, the DRLM and the economic sus-tainability reference model for digital assets implicitly men-tioned various factors and their implications for sustainabil-ity. These models have not considered the three dimensionsof sustainability per se, and the various research challengesand their implications for each form of sustainability; andthis is what is unique in the model proposed in this paper.The models proposed in this paper can be used as a researchframework to study various sustainability factors in the con-text of different types of digital libraries to explicitly identifythe role, and influence, of various actors and their interactions

in the context of the overall sustainability of digital libraries;and this calls for an integrated research approach.

Nathan [54] comments that information science, human–computer interaction, and participatory research approachescan help citizens develop practices that reduce negative eco-logical, economic, and social impacts of our informationpractices. The models proposed in this paper can be usedas a research framework to understand and study the vari-ous actors and their interactions that contribute to the eco-nomic, social and environmental sustainability of digitallibraries.

Reducing end-user ICT energy costs and promoting Greenuser behaviour [9] of individual users, and society at large,can play a big role in achieving the environmental sustain-ability of digital libraries. The sustainability models proposedhere suggest that all the stakeholders as well as the technolo-gies, knowledge, skills and culture of people should work inharmony to achieve the economic, social and environmen-tal sustainability of digital libraries. Overall, the model canserve as a starting point for future research and develop-ment with a holistic view of digital libraries, and the vari-ous factors that have implications for all the three forms ofsustainability.

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