Libraries have long served crucial roles in learning. The first great library, in Alexandria two thousand years ago was really the first university. It consisted of a zoo and various cultural artifacts in addition to much of the ancient world's written knowledge and attracted scholars from around the Mediterranean who lived and worked in a scholarly community for years at a time. Today, the rhetoric associated with the National/Global Information Infrastructure (N/GII) always includes examples of how the vast quantities of information that global networks provide (i.e., digital libraries) will be used in educational settings [16].

This paper describes how digital libraries are evolving to meet the needs of teaching and learning and identifies issues for continued development. We distinguish formal, informal, and professional learning and argue that digital libraries will allow teachers and students to use information resources and tools that have traditionally been physically and conceptually inaccessible. We illustrate the types of information resources that digital libraries offer to teachers and learners and discuss some of the issues and challenges that digital libraries present for teaching and learning.

A library is fundamentally an organized set of resources, which include human services as well as the entire spectrum of media (e.g., text, video, hypermedia). Libraries have physical components such as space, equipment, and storage media; intellectual components such as collection policies that determine what materials will be included and organizational schemes that determine how the collection is accessed; and people who manage the physical and intellectual components and interact with users to solve information problems.

Libraries serve at least three roles in learning. First, they serve a practical role in sharing expensive resources. Physical resources such as books and periodicals, films and videos, software and electronic databases, and specialized tools such as projectors, graphics equipment and cameras are shared by a community of users. Human resources--librarians (also called media specialists or information specialists) support instructional programs by responding to the requests of teachers and students (responsive service) and by initiating activities for teachers and students (proactive services). Responsive services include maintaining reserve materials, answering reference questions, providing bibliographic instruction, developing media packages, recommending books or films, and teaching users how to use materials. Proactive services include selective dissemination of information to faculty and students, initiating thematic events, collaborating with instructors to plan instruction, and introducing new instructional methods and tools. In these ways, libraries serve to allow instructors and students to share expensive materials and expertise.

Second, libraries serve a cultural role in preserving and organizing artifacts and ideas. Great works of literature, art, and science must be preserved and made accessible to future learners. Although libraries have traditionally been viewed as facilities for printed artifacts, primary and secondary school libraries often also serve as museums and laboratories. Libraries preserve objects through careful storage procedures, policies of borrowing and use, and repair and maintenance as needed. In addition to preservation, libraries ensure access to materials through indexes, catalogs, and other finding aids that allow learners to locate items appropriate to their needs.

Third, libraries serve social and intellectual roles in bringing together people and ideas. This is distinct from the practical role of sharing resources in that libraries provide a physical place for teachers and learners to meet outside the structure of the classroom, thus allowing people with different perspectives to interact in a knowledge space that is both larger and more general than that shared by any single discipline or affinity group. Browsing a catalog in a library provides a global view for people engaged in specialized study and offers opportunities for serendipitous insights or alternative views. In many respects, libraries serve as centers of interdisciplinarity--places shared by learners from all disciplines. Digital libraries extend such interdisciplinarity by making diverse information resources available beyond the physical space shared by groups of learners. One of the greatest benefits of digital libraries is bringing together people with formal, informal, and professional learning missions.

Formal learning is systematic and guided by instruction. Formal learning takes place in courses offered at schools of various kinds and in training courses or programs on the job. The important roles that libraries serve in formal learning are illustrated by their physical prominence on university campuses and the number of courses that make direct use of library services and materials. Most of the information resources in schools are tied directly to the instructional mission. Students or teachers who wish to find information outside this mission have in the past had to travel to other libraries. By making the broad range of information resources discussed below available to students and teachers in schools, digital libraries open new learning opportunities for global rather than strictly local communities.

Much learning in life is informal--opportunistic and strictly under the control of the learner. Learners take advantage of other people, mass media, and the immediate environment during informal learning. The public library system that developed in the U.S. in the late nineteenth century has been called the "free university", since public libraries were created to provide free access to the world's knowledge. Public libraries provide classic nonfiction books, a wide range of periodicals, reference sources, and audio and video tapes so that patrons can learn about topics of their own choosing at their own pace and style. Just as computing technology and world-wide telecommunications networks are beginning to change what is possible in formal classrooms, they are changing how individuals pursue personal learning missions.

Professional learning refers to the on going learning adults engage in to do their work and to improve their work-related knowledge and skills. In fact, for many professionals, learning is the central aspect of their work. Like informal learning, it is mainly self-directed, but unlike formal or informal learning, it is focused on a specific field closely linked to job performance, aims to be comprehensive, and is acquired and applied longitudinally. Since professional learning affects job performance, corporations and government agencies support libraries (often called information centers) with information resources specific to the goals of the organization. The main information resources for professional learning, however, are personal collections of books, reports, and files; subscriptions to journals; and the human networks of colleagues nurtured through professional meetings and various communications. Many of the data sets and computational tools of digital libraries were originally developed to enhance professional learning.

The information resources--both physical and human--that support these types of learning are customized for specific missions and have traditionally been physically separated, although common technologies such as printing, photography, and computing are found across all settings. This situation, is depicted in Figure 1.

Digital libraries combine technology and information resources to allow remote access, breaking down the physical barriers between resources. Although these resources will remain specialized to meet the needs of specific communities of learners, digital libraries will allow teachers and students to take advantage of wider ranges of materials and communicate with people outside the formal learning environment. This will allow more integration of the different types of learning, as depicted in Figure 2.

Although not all students or teachers in formal learning settings will use information resources beyond their circumscribed curriculum and not all professionals will want to interact even occasionally with novices, digital libraries will allow learners of all types to share resources, time and energy, and expertise to their mutual benefits. The following sections illustrate some of the types of information resources that are defining digital libraries.

An enormous amount of attention is being given to making data sets collected by scientific projects available to broader communities of users. International efforts such as the Earth Observing System (EOS) and the human genome project demand large investments of public resources and create huge volumes of data. Multiple forces act to cause the development of digital libraries of scientific data from these projects. First, the tools used to collect, transmit, and analyze data generate or require digital signals, thus the information materials are in digital form rather than paper form. Second, the data must be made available to scientists worldwide on a timely basis and digital electronic networks make this possible. Third, the huge public investments encourage scientists to disseminate data as widely as possible to maintain public support and further educational and social progress. Providing access to these data sets through electronic libraries is a important challenge, especially in the U.S. where law mandates that publicly supported scientific data be made freely available to citizens (see the sidebar by Gey).

One example of how primary data sets are used in education is the Earth System Science Community Curriculum Testbed project that links students and teachers in high schools and universities in an effort to build an earth system science (ESS) community (http://www.circles.org/ESSCC/ESSCC.GIF). The project aims to build a curriculum for the interdisciplinary field of ESS by linking teachers of physics, chemistry, biology and other sciences to ESS scientists and NASA data sets. Topics such as acid rain and global warming are explored by teams of students in each classroom by taking advantage of a growing electronic community of students, teachers, and researchers. Using tools such as Mosaic, FTP, and Stella, teachers and students in schools in North America access data sets at different levels of representation, analyze the data, simulate scenarios, collaborate with scientists and students at remote sites, and publish reports. This project has been funded as part of the NASA digital library initiative and illustrates how electronic technology can support collaboration among scientists and students and how digital libraries of data, messages, and student reports are grown and managed. The ESS community is thus manifested as an organic, evolving digital library that includes primary data sets, conversations about them, and the results of using them.

Textual databases of classic works (out of copyright) and image collections for important artistic exhibits or museums have been assembled by scholars and made available through the Internet. (See [13] for a collection of arts and humanities electronic resources and projects). As more schools and individuals acquire access tools and funds, it is likely that private digital libraries will move out of specialized markets to provide access to primary information for a fee. For-profit companies such as publishers of print, music, and film products and radio and television broadcasters own enormous volumes of information, and international information infrastructures will create new markets for that information. Teachers and learners will likely not be heavy on-demand users for this information but rather want to use it as the raw material for study and for integration into instructional presentations. How these materials are made available and what "fair use" policies evolve are yet to be determined.

Although electronic journals are becoming more common, they have not achieved as much penetration as many expected [23, 24]. As electronic journals develop, they will certainly improve informal and professional learning and will likely become useful resources in the K-12 arena which has traditionally maintained only modest journal collections in schools. Two common approaches to electronic journals are to: (i) store files in LaTeX, PostScript or ASCII form in a fileserver and email the files, or allow FTP access to them ("generic approach"); and (ii) store documents in hypertext/hypermedia systems and allow online browsing and perusal ("hypertext approach"). Table 1 gives a sample of electronic journals that use the generic approach and Table 2 gives a sample of those using the hypertext approach.

The main problems that these publications solve to different degrees are related to information retrieval support, display of complex graphics and formulas, and distribution speed and reliability. A recent journal using the "hypertext approach" is J.UCS, the Journal of Universal Computer Science (see http://www.iicm.tu-graz.ac.at/Cjucs_root or send an email for general information to jucs@iicm.tu-graz.ac.at with subject [info]). It addresses these three problems by using a range of searching techniques including scoped searches; using HFT, RTF and particularly LaTeX and PostScript as file formats to provide high quality display; and using a world-wide network of initially 65 "foundation servers" to remove much of the access-time problems associated with earlier attempts.

Perhaps the first examples of digital libraries in networked environments were the archives produced by the many USENET newsgroups and listservs available through global networks. News reading and filtering programs [21, 25] and search tools such as Archie and Veronica [8] provide rudimentary aids for locating information in these electronic discussions. Listservs are used for specialized projects (e.g., the ESS project above and the Perseus project both have listservs) and for distance education courses. In a cable television course taught by Marchionini, a listserv was used by students to present "one-minute papers" at the conclusion of each session. This provided continuity between sessions and personalized the interactions between the instructor and students, who would otherwise have only remote telephone access during live sessions. In another semester, students in graduate seminars in human-computer interaction taught by Marchionini at the University of Maryland and Christine Borgman at UCLA collaborated on term projects through email and FTP services. Students gained broader perspectives by virtue of the diversity in backgrounds that students from the different schools brought to the courses, and both positive collaborations and "techno-bullying" were observed. See [15] for a set of experiences in the virtual classroom.

In another setting, Maurer used Hyper-G [17] both as electronic library and discussion forum. In a 200-student class on "Societal Aspects of Computer Science" some 50 high-quality papers from specialists were made available to students via Hyper-G as the basis of a wide ranging electronic discussion. Students were able to comment on papers and earlier comments, the structure of the discussion being visualized using the X-Windows client Harmony [11]. The experiment created a network of over 4000 hyperlinked documents. Students remained "semi-anonymous" to encourage free discussion: i.e. students were allowed to choose arbitrary pen-names known only to each individual and to the instructor, the latter since student evaluation was based on the quality of contributions of the students. The experiment exemplifies blurring of the borderlines between electronic libraries and CSCW [7]--the semi-structured threads of conversation that make up news archives and lists provide another type of digital library product that will find increasing use in both formal and informal learning.

A variety of hypermedia materials are becoming available and these collections are often served from a library rather than dedicated machines in classrooms. The Perseus hypermedia corpus (2.0) includes about 200 plays, books, poems, and text fragments in Greek and English translation; almost 25,000 24-bit color images of vases, sculpture, coins, and sites; maps; site plans; and a variety of search, navigation, and display tools. [6, 20]. Hundreds of colleges and scores of high schools are currently using Perseus to support instruction in Greek language, ancient history, Greek literature, religion, archaeology, and art history. In many sites, Perseus is delivered through a campus network. In some sites, Perseus is provided on a stand-alone machine in a library. The many CD-ROM corpuses now available for specialized topics challenge schools and individuals to be judicious in acquisition and use of these materials, thus increasing the need for resource sharing functions of libraries.

Another instance of an emerging corpus of material entering digital libraries is the PC-library [19] a product developed by a publishing consortium. Originally designed for stand-alone PC applications it has now migrated to client/server architecture. At the time of writing some 40 substantial reference volumes including a 10-volume encyclopedia ("Meyer A-Z"), dictionaries for most European languages ("Langenscheidt dictionaries"), the famous German-English "Oxford Duden," and standard scientific reference books on medicine, computer science and CAD are either available or in preparation, some of them containing high quality diagrams and pictures. There are a number of aspects of the PC library particularly worth mentioning: First, an arbitrary subset of the books in the library can be "activated" at any time, and all searches (including fuzzy full text) are carried out only within the books activated. Second, the PC library is not just a set of static books but can be used in a variety of not-only-read mode: persons can leave comments (for themselves or for others); searches can be activated from other applications and the results used in such other applications; books can be augmented by additional (personal) entries, including multimedia material ( e.g. personal pictures or video clips); and material is automatically hyperlinked using a keyword based technique.

As vendors develop new products and as these specialized corpuses become available through global networks, libraries should take responsibility for ensuring secure and legal usage by students and teachers. One example of how libraries and computing centers cooperate today is in negotiating site licenses for these products and maintaining firewall services to ensure that licensing agreements are met. These collaborations can only grow as acquisition, organization, and dissemination of specialized software and hypermedia corpuses increase.

Numerische Mathematik Electronic Edition

Sponsor: Journal of the same name
Topics: Mathematics
Format: TeX and LaTeX
Features: every electronic issue some 2 weeks before the printed issue.
Access: EM-Helpdesk@springer.de.

Electronic Publication

Sponsor: MIT
Topics: Theoretical computer science
Format: LaTeX or PostScript
Features: Subscribers receive a notice each time an article is published;
available for FTP
Access: Fisher@mitvma.mit.edu.

EJournal

Asia-Pacific Journal (APEX-J)

Digest of Physics News Items

Table 2. Selected Electronic Journals Providing Hypertext Access

MUSE

Journal of Computer-Mediated Communication (JCMC)

Electronic Journal of Combinatorics

Newsletter of the National Research Center on Student Learning (NRCSL).

Journal of Universal Computer Science (JUCS)

There are a host of bibliographic and catalog databases that may be included in digital libraries. These range from the more than 20 million record database of bibliographic citations in OCLC and the millions of citations in online databases for specialized literatures such as medicine (e.g., MEDLINE) and engineering (e.g., NTIS). Tertiary databases such as citation indexes and databases of directories make information seeking more effective but require specific skill and effort on the part of information seekers. Many of the thesauri for specialized literatures are available in electronic form (e.g., Medical Subject Headings, ACM Computing Reviews Classification System) and techniques for merging and filtering these languages to allow users to search across multiple databases are emerging. Although most indexes to image and sound collections currently use words from captions or titles, new pattern-matching techniques are emerging to categorize and classify multimedia objects [10]. In the past, bibliographic instruction has been provided by librarians as a supplement to "regular" courses, but widespread availability of digital libraries will require remote instruction and support related to information-seeking skills and knowledge.

It often has been said that the Internet is starting to provide the largest library humankind has ever had. As true as this may be, it is also the messiest library that ever has existed. Navigation and display tools such as Mosaic allow users to browse the World Wide Web and display text and multimedia objects. Search tools such as the Wide Area Information Server (WAIS) and Archie and Veronica allow people to search specific directories or list archives (see [22] for an overview of tools). However, in addition to index and directory services or navigation tools, it has become apparent that such 'a posteriori' tools to organize the unstructured Internet universe are not sufficient. Rather, some 'a priori' structuring is necessary. This was first done quite successfully with Gopher [3] and later with WWW [5]. However, "first generation hypermedia techniques" do not seem to be sufficient for large amounts of data: "second generation techniques" [4] involving distributed database mechanisms, scope definition facilities for searches, bidirectional link databases [14] for automatic link maintenance, and other advanced techniques are emerging. For example, Harmony [11], the X-Windows client for Hyper-G, WWW, Gopher and WAIS provides sophisticated navigational facilities when used in conjunction with a Hyper-G database: the facilities include visual "local maps" of all in- and outgoing hyperlinks, a 3-D landscape generator, a history and hierarchy browser, Boolean searches on attributes, full text searches including approximate matches in user-defined scopes that may arbitrarily cross even the physical boundaries of servers. Such features will make working with large electronic libraries less frustrating than it is sometimes now, and will certainly assure that the use of electronic libraries is more efficient than using large amounts of printed material. As these tools evolve, better integration of search and display will be necessary. One approach is dynamic queries [2] that provide graphical representations for database elements and sliders for adjusting parameters on those elements. As parameters are changed, the graphical display is immediately updated, providing immediate visual answer sets.

The examples above illustrate that digital libraries have obvious roles to play in formal learning settings by providing teachers and learners with knowledge bases in a variety of media. In addition to expanding the format of information (e.g., multimedia, simulations), digital libraries offer more information than most individuals or schools have been able to acquire and maintain. Digital libraries are accessible in classrooms and from homes as well as in central library facilities where specialized access, display, and use tools may be shared. Remote access allows possibilities for vicarious field trips, virtual guest speakers, and access to rare and unique materials in classrooms and at home. The promise is one of better learning through broader, faster, and better information and communication services. These physical advantages promise several advantages to teachers and learners by extending the classroom, however, as with all technologies, there are costs and tradeoffs to these advantages.

One clear difference between traditional libraries and digital libraries is that digital libraries offer greater opportunity for users to deposit information as well as use information. Thus, students and teachers can easily be publishers as well as readers in digital libraries. The number of student-produced "Mosaic home pages" and gopher sites continues to grow as teachers and students not only bring digital library information into the classroom but move the products of the classroom out into the digital libraries. Just as distinctions between publishers and readers are becoming less clear in networked environments, Internet access in classrooms blurs distinctions between teaching and learning. Students bring interesting and important information to class discussions and in many cases lead teachers and classmates to new electronic resources and tools. Teachers' increasingly will find themselves in the important roles of moderator and critic, modeling for students how to examine and compare points of view and look critically at information. Teachers who have begun using networked materials in their classes are early adopters of new ideas and technologies and are comfortable sharing power with students. Just as "authority of information" has become an issue in professional communities that leverage networks, the authority of information in classrooms that has traditionally rested solely with teachers will increasingly be challenged by students locally and remotely.

Digital libraries will support communities of interest and allow more specialized courses to be offered. For example, students at different high schools in the CoVis project collaborated by sharing a digital library of weather data [12] and students in the Earth System Science Community Project described above share a variety of NASA data in classes in Washington D.C., St. Louis, Los Angeles, and New Mexico. Telecourses have already allowed rural schools to offer advanced placement courses to a few students by sharing teachers across geographical distances. As network access improves in schools, highly specialized courses offered on a distributed basis will become common, and it is likely that some of these will be offered by students. Internet-based courses have already been offered successfully, although mainly on the topic of the Internet itself, and network based electronic conferences have proven effective (e.g., University of Maryland Professor, Thomas O'Haver recently ran a chemistry conference that involved 450 participants from 33 countries).

The most important changes that digital libraries bring may be in advancing informal learning. The same advantages that accrue to classroom learning also accrue to individuals pursuing their own learning. In many ways, the development of Freenets are extensions of the public library system. Digital libraries are digital schools that offer formal packaging for specific skills and topics as well as general browsing for creative discovery and self-guided, informal learning. The design community has already begun to consider ways to support learning on demand in electronic environments [9] to address problems of coverage (since no learning system can cover all things learners may need) and obsolescence (systems and knowledge changes).

For the promises to obtain, issues of access and intellectual property must be addressed. Although the U.S. Library of Congress has committed to becoming a digital library, it can make available only documents or finding aides created within the Library or government agencies, items out of copyright, and representations from exhibits or events sponsored by the Library. Although these represent enormous quantities of information, the core holdings of the Library--the books, films, and recording--cannot be made available electronically under current copyright law. Whether the copyright law will change to allow materials to be accessed electronically under some educational fair use arrangement remains to be settled. Curators, theater owners and publishers are loathe to give up restricted access due to understandable self-preservation concerns. Some of these fears may be unfounded. For example, in the 1930's owners of professional baseball clubs allowed only World Series games to be broadcast on the radio because they feared that attendance at regular games would go down if all games were broadcast. When Lawrence McFale in Cincinnati began to broadcast the Reds' games in 1938, entire new markets opened up beyond the traditional male attendees--women and men who previously did not know much about baseball became interested and attendance went up (Ken Burns' PBS series, Baseball). Additionally, entire new revenue streams from advertising became available, which today eclipse attendance profits. However, historical examples are not likely to be enough to convince publishers and other information industry entities to make their "property" available electronically without secure mechanisms for profit.

Even more challenging, however, is building intellectual infrastructures for digital libraries. These include techniques for using electronic information in teaching and learning [18]. Teachers must learn how to teach with multimedia resources and to share informational authority with students. Designing activities that take advantage of digital library resources requires time and effort to examine what is available and integrate information into modules and sequences appropriate to the students and curriculum. Furthermore, modeling the research process for students requires teachers to grapple with problems on-the-fly, make mistakes, recover, react to dead ends, and demonstrate all the other uncomfortable and frustrating aspects of problem solving. Like Euclid, who presented the products of geometric research in the form of neat, polished deductive proofs (rather than the empirical and intuitive thought that led to the theorems), teachers are more comfortable providing polished packages/modules rather than the messy details of discovery and problem solving. Applying digital libraries in classrooms requires different attitudes and tolerances for such learning conditions.

Just as teachers must learn new strategies for using electronic tools in teaching, students must learn how to learn with multimedia (both actively and passively) and how to take increased responsibility for directing their own learning. In our observations of students in classrooms where Perseus was used, students expressed concerns about taking notes--because a screen of text, a screen of vases, and the instructor's verbal comments were concurrently available, they did not know what to write down! Although better technological tools such as networked laptop computers may solve the technical problem, the issues of what to attend to and how multiple streams of information should be integrated require new combinations of perceptual, cognitive, and physical skills for learning. In short, building intellectual infrastructures requires intellectual, emotional, and social breakthroughs for teaching and learning.

At the nexus of physical and intellectual infrastructure is the interface to the digital library. Tools for finding, managing, using, and publishing electronic information must be both powerful and easy to use. Digital libraries must provide a mix of software and people to provide reference assistance and question answering services (e.g., Ackerman's Answer Garden system for handling X-Windows questions, [1]). The people in the digital library will go beyond reference to serve as teachers on demand. These humans must be aided by software that shunt "typical" questions toward pathfinders or frequently-asked-question services. Thus, digital libraries will extend what has been the most beneficial feature of electronic networks--communication---to teaching and learning settings. Good interfaces will allow learners to take advantage of digital resources equally well in classrooms, homes, and offices.

Clearly, digital libraries have important roles to play in teaching and learning. Existing physical schools and libraries will continue to exist since they serve cultural and social roles as well as informational roles. There will always be a need for physical objects and social settings in learning; the vicarious is not enough. Parents will continue to demand child care, assurances of organized and shared culture beyond television, and human direction and guidance in learning at all levels. These demands will also be augmented by digital environments. Digital libraries will allow parents, teachers, and students to share common information resources and communicate easily as needed. In special cases, work, school, and play may become one--novice and professional learners collaborating with common information resources to solve real problems. In many respects, digital libraries will become digital schools. This represents a return to Alexandria, where learners of all types come together to share and explore information and expertise.

1. Ackerman, M.S. Answer Garden: A tool for growing organizational memory. Ph.D. Thesis, MIT, 1993.
2. Ahlberg, C., Williamson, C., & Shneiderman, B. Dynamic queries for information exploration: An implementation and evaluation. In B. Shneiderman (Ed.). The sparks of innovation in human-computer interaction. Ablex, Norwood, NJ. 1994, pp. 281-294.
3. Alberti, B., Anklesaria, F., Lindnder, P., McCahill, M., &Torrey, D. Internet Gopher Protocol: A Distributed Document Search and Retrieval Protocol; FTP from boombox.micro.umn.edu, directory pub/gopher/gopher_protocol. 1994.
4. Andrews, K., Kappe, F., Maurer, H., Schmaranz, K. On Second Generation Hypermedia Systems, IIG Report, Graz (1994); FTP server iicm.tu-graz.ac.at directory pub/Hyper-G/papers.
5. Berners-Lee, T., Cailliau, R., Groff, J. WorldWideWeb: The Information Universe, Electronic Networking: Research, Applications and Policy 1,2 (1992), 52-58.
6. Crane, G. Perseus 2.0. New Haven, CT: Yale University Press. 1994.
7. Devan, P. A Survey of Applications of CSCW Including Some in Educational Settings, Proceedings of ED-MEDIA'93, (June 23-26, Orlando, FL). AACE, Charlottesville, VA, 1993, pp. 147-152.
8. Deutsch,P. Resource Discovery in an Internet Environment-the Archie Approach, Electronic Networking:Research,Applications and Policy 1,2 (1992), 45-51.
9. Eisenberg, M. & Fischer, G. Symposium: Learning on demand. Proceedings of the 15th Annual Conference of the Cognitive Science Society, (June 18-20, Boulder, CO), Erlbaum, Hillsdale, NJ, 1993, pp. 180- 186.
10. Faloutsos, C., Equitz, W., Flickner, M., Niblack, W., Petkovic, D., & Barber, R. Efficient and effective querying by image content, Journal of Intelligent Information Systems, in press.
11. Fenn,B., Maurer,H.: Harmony on an Expanding Net; ACM Interactions. 1,3, (October 1994), 26-38
12. Fishman, B.J. & D'Amico, L.M. Which way will the wind blow? Networked computer tools for studying the weather. Proceedings of ED-MEDIA 94 (June 25-30,Vancouver, BC). AACE, Charlottesville, VA, 1994, pp. 209-216.
13. Getty Art History Information Program, The American Council of Learned Societies, & The Coalition for Networked Information. Humanities and arts on the information highways: A profile. Santa Monica, CA: Getty Art History Information Program. (1994).
14. Haan,B.J., Kahn,P., Riley,V.A., Coombs,J.H., Meyrowitz,N.K. IRIS Hypermedia Services, Communications of the ACM 35,1 (1992), 36-51.
15. Hiltz, S.R., & Turoff, M.. Virtual classroom plus video: Technology for educational excellence. Proceedings of ED-MEDIA 94 (June 25-30,Vancouver, BC). AACE, Charlottesville, VA, 1994, pp. 26-31.
16. Information Infrastructure Task Force. The national information infrastructure: Agenda for action. Washington, DC: NTIA. 1993, Also available via anonymous ftp from ftp.ntia.doc.gov.
17. Kappe,F., Maurer,H., Scherbakov,N. Hyper-G-a Universal Hypermedia System, Journal of Educational Multimedia and Hypermedia 2,1 (1993), 39-66.
18. Marchionini, G. & Crane, G. Evaluating hypermedia and learning: Methods and results from the Perseus Project. ACM Transactions on Information Systems, 12(1), (1994), 5-34.
19. Maurer, H., Muelner,H., Schneider, A: The PC Library and Applications in an Educational Setting, Symposium Didaktik der Mathematik, Klagenfurt (1994)
20. Mylonas, E. An interface to classical Greek civilization. Journal of the American Society for Information Science, 43(2), (1992), 192---201.
21. Oard, D.W. The Information Filtering Laboratory. 1994. WWW site: http://www.umiacs.umd.edu/labs/CLIP/filter.html.
22. Obraczka, K., & Danzig, P., & Li, S. Internet resource discovery services. IEEE Computer, 26, (1993), 8-22.
23. Odlyzko, A., M. Tragic Loss or Good Riddance? The impending demise of traditional scholarly journal, To appear in: Notices of the AMS (1994).
24. Schaffner, A. The future of scientific journals: Lessons from the past. Information Technology and Libraries, 13(4), 1994, 239-247.
25. Stevens, C. Knowledge-Based Assistance for Handling Large, Poorly Structured Information Spaces. Ph.D. Dissertation, University of Colorado at Boulder Technical Report Number CU-CS-640-93, January 1993.