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RFC 1614

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Network Access to Multimedia Information

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Network Working Group                                            C. Adie
Request for Comments: 1614        Edinburgh University Computing Service
RARE Technical Report: 8                                        May 1994
Category: Informational

                Network Access to Multimedia Information

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.


   This report summarises the requirements of research and academic
   network users for network access to multimedia information.  It does
   this by investigating some of the projects planned or currently
   underway in the community.  Existing information systems such as
   Gopher, WAIS and World-Wide Web are examined from the point of view
   of multimedia support, and some interesting hypermedia systems
   emerging from the research community are also studied.  Relevant
   existing and developing standards in this area are discussed.  The
   report identifies the gaps between the capabilities of
   currentlydeployed systems and the user requirements, and proposes
   further work centred on the World-Wide Web system to rectify this.

   The report is in some places very detailed, so it is preceded by an
   extended summary, which outlines the findings of the report.

Publication History

   The first edition was released on 29 June 1993.  This second edition
   contains minor changes, corrections and updates.

Table of Contents

    Acknowledgements                                                2
    Disclaimer                                                      2
    Availability                                                    3
    0. Extended Summary                                             3
    1. Introduction                                                10
      1.1. Background                                              10
      1.2. Terminology                                             11
    2. User Requirements                                           13
      2.1. Applications                                            13
      2.2. Data Characteristics                                    18

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      2.3. Requirements Definition                                 19
    3. Existing Systems                                            24
      3.1. Gopher                                                  24
      3.2. Wide Area Information Server                            30
      3.3. World-Wide Web                                          34
      3.4. Evaluating Existing Tools                               42
    4. Research                                                    47
      4.1. Hyper-G                                                 47
      4.2. Microcosm                                               48
      4.3. AthenaMuse 2                                            50
      4.4. CEC Research Programmes                                 51
      4.5. Other                                                   53
    5. Standards                                                   55
      5.1. Structuring Standards                                   55
      5.2. Access Mechanisms                                       62
      5.3. Other Standards                                         63
      5.4. Trade Associations                                      66
    6. Future Directions                                           68
      6.1. General Comments on the State-of-the-Art                68
      6.2. Quality of Service                                      70
      6.3. Recommended Further Work                                71
    7. References                                                  76
    8. Security Considerations                                     79
    9. Author's Address                                            79


   The following people have (knowingly or unknowingly) helped in the
   preparation of this report: Tim Berners-Lee, John Dyer, Aydin Edguer,
   Anton Eliens, Tony Gibbons, Stewart Granger, Wendy Hall, Gary Hill,
   Brian Marquardt, Gunnar Moan, Michael Neuman, Ari Ollikainen, David
   Pullinger, John Smith, Edward Vielmetti, and Jane Williams.  The
   useful role which NCSA's XMosaic information browser tool played in
   assembling the information on which this report was based should also
   be acknowledged - many thanks to its developers.

   All trademarks are hereby acknowledged as being the property of their
   respective owners.


   This report is based on information supplied to or obtained by
   Edinburgh University Computing Service (EUCS) in good faith.  Neither
   EUCS nor RARE nor any of their staff may be held liable for any
   inaccuracies or omissions, or any loss or damage arising from or out
   of the use of this report.

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   The opinions expressed in this report are personal opinions of the
   author.  They do not necessarily represent the policy either of RARE
   or of ECUS.

   Mention of a product in this report does not constitute endorsement
   either by EUCS or by RARE.


   This document is available in various forms (PostScript, text,
   Microsoft Word for Windows 2) by anonymous FTP through the following

    Paper copies are available from the RARE Secretariat.

0. Extended Summary


   This report is concerned with issues in the intersection of
   networked information retrieval, database and multimedia
   technologies.  It aims to establish research and academic user
   requirements for network access to multimedia data, to look at
   existing systems which offer partial solutions, and to identify
   what needs to be done to satisfy the most pressing requirements.

   User Requirements

   There are a number of reasons why multimedia data may need to be
   accessed remotely (as opposed to physically distributing the data,
   e.g., on CD-ROM).  These reasons centre on the cost of physical
   distribution, versus the timeliness of network distribution.  Of
   course, there is a cost associated with network distribution, but
   this tends to be hidden from the end user.

   User requirements have been determined by studying existing and
   proposed projects involving networked multimedia data.  It has
   proved convenient to divide the applications into four classes
   according to their requirements: multimedia database applications,
   academic (particularly scientific) publishing applications, cal
   (computeraided learning), and general multimedia information

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   Database applications typically involve large collections of
   monomedia (non-text) data with associated textual and numeric
   fields. They require a range of search and retrieval techniques.

   Publishing applications require a range of media types,
   hyperlinking, and the capability to access the same data using
   different access paradigms (search, browse, hierarchical, links).
   Authentication and charging facilities are required.

   Cal applications require sophisticated presentation and
   synchronisation capabilities, of the type found in existing
   multimedia authoring tools.  Authentication and monitoring
   facilities are required.

   General multimedia information services include on-line
   documentation, campus-wide information systems, and other systems
   which don't conveniently fall into the preceding categories.
   Hyperlinking is perhaps the most common requirement in this area.

   The analysis of these application areas allows a number of
   important user requirements to be identified:

      o    Support for the Apple Macintosh, UNIX and PC/MS Windows

      o    Support for a wide range of media types - text, image,
           graphics and application-specific media being most
           important, followed by video and sound.

      o    Support for hyperlinking, and for multiple access structures
           to be built on the same underlying data.

      o    Support for sophisticated synchronisation and presentation

      o    Support for a range of database searching techniques.

      o    Support for user annotation of information, and for user-
           controlled display of sequenced media.

      o    Adequate responsiveness - the maximum time taken to retrieve
           a node should not exceed 20s.

      o    Support for user authentication, a charging mechanism, and
           monitoring facilities.

      o    The ability to execute scripts.

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      o    Support for mail-based access to multimedia documents, and
           (where appropriate) for printing multimedia documents.

      o    Powerful, easy-to-use authoring tools.

   Existing Systems

   The main information retrieval systems in use on the Internet are
   Gopher, Wais, and the World-Wide Web.  All work on a client-server
   paradigm, and all provide some degree of support for multimedia data.

   Gopher presents the user with a hierarchical arrangement of nodes
   which are either directories (menus), leaf nodes (documents
   containing text or other media types), or search nodes (allowing some
   set of documents to be searched using keywords, possibly using WAIS).
   A range of media types is supported.  Extensions currently being
   developed for Gopher (Gopher+) provide better support for multimedia
   data.  Gopher has a very high penetration (there are over 1000 Gopher
   servers on the Internet), but it does not provide hyperlinks and is
   inflexibly hierarchical.

   Wais (Wide Area Information Server) allows users to search for
   documents in remote databases.  Full-text indexing of the databases
   allows all documents containing particular (combinations of) words to
   be identified and retrieved.  Non-text data (principally image data)
   can be handled, but indexing such documents is only performed on the
   document file name, severely limiting its usefulness.  However, WAIS
   is ideally suited to text search applications.

   World-Wide Web (WWW) is a large-scale distributed hypermedia system.
   The Web consists of nodes (also called documents) and links.  Links
   are connections between documents: to follow a link, the user clicks
   on a highlighted word in the source document, which causes the
   linkedto document to be retrieved and displayed.  A document can be
   one of a variety of media types, or it can be a search node in a
   similar sense to Gopher.  The WWW addressing method means that WAIS
   and Gopher servers may also be accessed from (indeed, form part of)
   the Web.  WWW has a smaller penetration than Gopher, but is growing
   faster.  The Web technology is currently being revised to take better
   account of the needs of multimedia information.

   These systems all go some way to meet the user requirements.

      o    Support for multiple platforms and for a wide range of media
           types (through "viewer" software external to the client
           program) is good.

      o    Only WWW has hyperlinks.

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      o    There is little or no support for sophisticated presentation
           and synchronisation requirements.

      o    Support for database querying tends to be limited to
           "keyword" searches, but current developments in Gopher and
           WWW should make more sophisticated queries possible.

      o    Some clients support user annotation of documents.

      o    Response times for all three systems vary substantially
           depending on the network distance between client and server,
           and there is no support for isochronous data transfer.

      o    There is little in the way of authentication, charging and
           monitoring facilities, although these are planned for WWW.

      o    Scripting is not supported because of security issues

      o    WWW supports a mail responder.

      o    The only system sufficiently complex to warrant an authoring
           tool is WWW, which has editors to support its hypertext
           markup language.


   There are a number of research projects which are of significant

   Hyper-G is an ambitious distributed hypermedia research project at
   the University of Graz.  It combines concepts of hypermedia,
   information retrieval systems and documentation systems with aspects
   of communication and collaboration, and computer-supported teaching
   and learning.  Automatic generation of hyperlinks is supported, and
   there is a concept of generic structures which can exist in parallel
   with the hyperlink structure.  Hyper-G is based on UNIX, and is in
   use as a CWIS at Graz.  Gateways between Hyper-G and WWW exist.

   Microcosm is a PC-based hypermedia system developed at the University
   of Southampton.  It can be viewed as an integrating hypermedia
   framework - a layer on top of a range of existing applications which
   enables relationships between different documents to be established.
   Hyperlinks are maintained separately from the data.  Networking
   support for Microcosm is currently under development, as are versions
   of Microcosm for the Apple Macintosh and for UNIX.  Microcosm is
   currently being "commercialised".

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   AthenaMuse 2 is an ambitious distributed hypermedia authoring and
   presentation system under development by a university/industry
   consortium based at MIT.  It will have good facilities for
   presentation and synchronisation of multimedia data, strong authoring
   support, and will include support for networking isochronous data. It
   will be a commercial product.  Initial versions will support UNIX and
   X windows, with a PC/MS Windows version following.  Apple Macintosh
   support has lower priority.

   The "Xanadu" project is designing and building an "open, social
   hypermedia" distributed environment, but shows no sign of delivering
   anything after several years of work.

   The European Commission sponsors a number of peripherally relevant
   projects through its Esprit and RACE research programmes.  These
   programmes tend to be oriented towards commercial markets, and are
   thus not directly relevant.  An exception is the Esprit IDOMENEUS
   project, which brings together workers in the database, information
   retrieval and multimedia fields.  It is recommended that RARE
   establish a liaison with this project.

   There are a variety of other academic and commercial research
   projects which are also of interest.  None of them are as directly
   relevant as those outlined above.


   There are a number of existing and emerging standards for structuring
   hypermedia applications.  Of these, the most important are SGML,
   HyTime, MHEG, ODA, PREMO and Acrobat.  All bar the last are de jure
   standards, while Acrobat is a commercial product which is being
   proposed as a de facto standard.

   SGML (Standard Generalized Markup Language) is a markup language for
   delimiting the logical and semantic content of text documents.
   Because of its flexibility, it has become an important tool in
   hypermedia systems.  HyTime is an ISO standardised infrastructure for
   representing integrated, open hypermedia documents, and is based on
   SGML.  HyTime has great expressive power, but is not optimised for
   run-time efficiency.  It is recommended that future RARE work on
   networked hypermedia should take account of the importance of SGML
   and HyTime.

   MHEG (Multimedia and Hypermedia information coding Experts Group) is
   a draft ISO standard for representing hypermedia applications in a
   platform-independent form.  It uses an object-oriented approach, and
   is optimised for run-time efficiency.  Full IS status for MHEG is
   expected in 1994.  It is recommended that RARE keep a watching brief

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   on MHEG.

   The ODA (Open Document Architecture) standard is being enhanced to
   incorporate multimedia and hypermedia features.  However, interest in
   ODA is perceived to be decreasing, and it is recommended that ODA
   should not form a basis for further RARE work in networked

   PREMO is a new work item in the ISO graphics standardisation
   community, which appears to overlap with MHEG and HyTime.  It is not
   clear that the PREMO work, which is at a very early stage, is
   worthwhile in view of the existence of those standards.

   Acrobat PDF is a format for representing multimedia (printable)
   documents in a portable, revisable form.  It is based on Postscript,
   and is being proposed by Adobe Inc (originators of Postscript) as an
   industry standard.  RARE should maintain awareness of this technology
   in view of its potential impact on multimedia information systems.

   There are various standards which have relevance to the way
   multimedia data is accessed across the network.  Many of these have
   been described in a previous report [1].  Two further access
   protocols are the proposed multimedia extensions to SQL, and the
   Document Filing and Retrieval protocol.  Neither of these are likely
   to have major significance for networked multimedia information

   Other standards of importance include:

      o    MIME, a multimedia email standard which defines a range of
           media types and encoding methods for those types which are
           useful in a wider context.

      o    AVIs (Audio-Visual Interactive services) and the associated
           multimedia scripting language SMSL, which form a
           standardisation initiative within CCITT (now ITU-TSS) to
           specify interactive multimedia services which can be
           provided across telephone/ISDN networks.

   There are two important trade associations which are involved in
   standardisation work.  The Interactive Multimedia Association (IMA)
   has a Compatibility Project which is developing a specification for
   platform-independent interactive multimedia systems, including
   networking aspects.  A newly-formed group, the Multimedia
   Communications Forum (MMCF), plans to provide input to the standards
   bodies.  It is recommended that RARE become an Observing Member of
   the MMCF.  A third trade association - the Multimedia Communications
   Community of Interest - has also just been formed.

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   Future Directions

   Three common design approaches emerge from the variety of systems and
   standards analysed in this report.  They can be described in terms of
   distinctions between different aspects of the system:

      o    content is distinct from hyperstructure

      o    media type is distinct from media encoding

      o    data is distinct from protocol

   Distributed hypermedia systems are emerging from the
   research/development phase into the experimental deployment phase.
   However, the existing global information systems (Gopher, WAIS and
   WWW) are still largely limited to the use of external viewers for
   nontextual data.  The most significant mismatches between the
   capabilities of currently-deployed systems and user requirements are
   in the areas of presentation and quality of service (i.e.,

   Improving QOS is significantly more difficult than improving
   presentation capabilities, but there are a number of possible ways in
   which this could be addressed.  Improving feedback to the user,
   greater multi-threading of applications, pre-fetching, caching, the
   use of alternative "views" of a node, and the use of isochronous data
   streams are all avenues which are worth exploring.

   In order to address these problems, it is recommended that RARE seek
   to adapt and enhance existing tools, rather than develop new ones.

   In particular, it is recommended that RARE select the World-Wide Web
   to concentrate its efforts on.  The reasons for this choice revolve
   around the flexibility of the WWW design, the availability of
   hyperlinks, the existing effort which is already going into
   multimedia support in WWW, the fact that it is an integrating
   solution incorporating both WAIS and Gopher support, and its high
   rate of growth compared to Gopher (despite Gopher's wider
   deployment).  Gopher is the main competitor to WWW, but its
   inflexibly hierarchical structure and the absence of hyperlinks make
   it difficult to use for highly-interactive multimedia applications.

   It is recommended that RARE should invite proposals for and
   subsequently commission work to:

      o    Develop conversion tools from commercial multimedia
           authoring packages to WWW, and accompanying authoring

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      o    Implement and evaluate the most promising ways of overcoming
           the QOS problem.

      o    Implement a specific user project using these tools, to
           validate that the facilities being developed are truly
           relevant to real applications.

      o    Use the experience gained to inform and influence the
           development of the WWW technology.

      o    Contribute to the development of PC/MS Windows and Apple
           Macintosh WWW clients, particularly in the multimedia data
           handling area.

   It is noted that the rapid growth of WWW may in the future lead to
   problems through the implementation of multiple, uncoordinated and
   mutually incompatible add-on features.  To guard against this trend,
   it may be appropriate for RARE, in coordination with CERN and other
   interested parties such as NCSA, to:

      o    Encourage the formation of a consortium to coordinate WWW
           technical development.

1. Introduction

1.1. Background

   This study was inspired by the realisation that while some aspects of
   distributed multimedia technology are being actively introduced into
   the European research community (for instance, audiovisual
   conferencing, through the MICE project), other aspects are receiving
   less attention.  In particular, one category in which there seems to
   be relatively little activity is providing solutions to ease remote
   access to multimedia resources (for instance, accessing stored
   audio/video clips or images, or indeed entire multimedia
   applications, across the network).  Few commercial products address
   this, and the relevance of existing standards in this area is

   Of the 50 or so research projects documented in the recent RARE
   distributed multimedia survey [1], only about six have a direct
   relevance to this application area.  Where stated in the survey, the
   main research effort in these projects is often directed towards the
   "difficult" problems, such as the transfer of isochronous data and
   the design and implementation of object-oriented multimedia
   databases, rather than towards user-oriented issues.

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   This report is concerned with practical issues in the intersection of
   networked information retrieval, database and multimedia
   technologies.  It aims to establish actual user requirements in this
   area, to look at existing systems which offer partial solutions, and
   to identify what additional work needs to be done to satisfy the most
   pressing requirements.

1.2. Terminology

   In order to discuss multimedia information systems, we need a
   consistent terminology.  The vocabulary defined below embodies some
   of the concepts of the Dexter hypertext reference model [2].  This
   model is sufficiently general to be useful for describing most of the
   facilities and requirements of the multimedia information systems
   described in this report.  (However, the Dexter model does not
   describe searchable index objects - it is not a database reference

    anchor             An identified portion of a node.  E.g., in a text
                       node, an anchor might be a string of one or more
                       adjacent characters, while in an image node it
                       might be a rectangular area of the image.

    composite node     A node containing data of multiple media types.

    document           Often used loosely as a synonym for node.

    hyperdocument      We refer to a collection of related nodes,
                       linked internally with hyperlinks, as a
                       "hyperdocument".  Examples are a database of
                       medical images and associated text; a module
                       from a suite of teaching material; or an article
                       in a scientific journal.  A hyperdocument may
                       contain hyperlinks to other data which exists in
                       internally with hyperlinks, as a
                       "hyperdocument". Examples are a other
                       hyperdocuments, but can be viewed as largely
                       self-contained.  It is a highlevel "unit of
                       authoring", but is not necessarily perceived as
                       a distinct unit by a reader (although it may be
                       so perceived, particularly if it contains few
                       hyperlinks to outside entities).

    hyperlink          Set of one or more source anchors and one or
                       more target anchors.  Also known simply as a

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    isochronous (adjective) Describes a continuous flow of data which
                       is required to be delivered by the network under
                       critical time constraints.

    leaf node          A node which contains no source anchors.

    media type         An attribute of data which describes the general
                       nature of its expected presentation.  The value
                       of this attribute could be one of the following
                       (not exhaustive) list:

                       o Text

                       o Sound

                       o Image (e.g., a "photograph")

                       o Graphics (e.g., a "drawing")

                       o Animation (i.e., moving graphics)

                       o Movie (i.e., moving image)

    monomedia (adjective)   Said of data which is all of the same media

    multimedia (adjective)  Said of data which contains different media
                       types.  This definition is stricter than general
                       usage, where "multimedia" is often  used as a
                       generic term for non-textual data, and where it
                       may even be used as a noun.

    physical media     Magnetic or optical storage.  Not to be confused
                       with media type!

    [simple] node      A monomedia object which may be retrieved and
                       displayed as a single unit.

    source anchor      An anchor which may be "actioned" by the user,
                       causing the node(s) containing the target
                       anchor(s) in the same hyperlink to be retrieved
                       and displayed.  This process is called
                       "traversing the link".

    target anchor      an anchor forming part of a hyperlink, whose
                       containing node is retrieved and displayed when
                       the hyperlink is traversed.

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2. User Requirements

   User requirements in an area such as networking, which is subject to
   rapid technological change, are sometimes difficult to identify.  To
   an extent, technology leads applications, and users will exploit what
   is possible.

2.1. Applications

   Awareness of the range of networked multimedia applications which are
   currently being envisaged by computer users in the academic and
   research community leads to a better understanding of the technical
   requirements.  This section outlines some projects which require
   remote access to multimedia information across research networks, and
   which are currently either at a preliminary stage or underway.  The
   projects are divided into broad categories according to their

   Multimedia Databases

   Here are several examples of multimedia projects which have a
   "database" character.

   The Peirce Telecommunity Project

      This project centres on the construction of a multimedia (text and
      image) database of the works of the American philosopher Peirce,
      together with tools to process the data and to make it available
      over the Internet.  A sub-project at Brown University focuses on
      adapting existing client/server network tools for this purpose.
      The requirements for network access include facilities for
      structured viewing, intelligent retrieval, navigation, linking,
      and annotation, as well as for domainspecific processing.

   Museum Object Databases

      The RAMA (Remote Access to Museum Archives) project is funded
      under the EEC RACE II programme.  Its objective is to develop a
      system which allows museums to make multimedia information about
      their exhibits and archived material available over an ISDN
      network.  The requirements capture and technical architecture
      design phases are now complete, and a prototype system will be
      delivered in June 1993 to link the Ashmolean Museum (Oxford, GB),
      the Musee d'Orsay (Paris, FR) and the Museum Archeological
      National (Madrid, ES).  Image data is the main media type of
      interest, although video and sound may also play a part.

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   The Bristol Biomedical Videodisk Project

      The Bristol Biomedical Videodisc is a collection of Medical,
      Veterinary and Dental images.  The collection holds some 24,000
      still images and is continuously growing.  Textual information
      regarding the images is included as part of the database and this
      can be searched on any keyword, number or other data type, or a
      combination of any of these.  The images are currently delivered
      in analogue form on a videodisc, but many institutions are unable
      to afford the cost of videodisc players.  Investigations into
      making this image and text database available across the network
      are underway.


      ArchiGopher is a Gopher server at the College of Architecture,
      University of Michigan, dedicated to the dissemination of
      architectural knowledge.  Presently in its infancy, ArchiGopher is
      intended to become a multimedia resource for all architecture
      faculty and students world-wide.  Some of the available or planned
      resources are:

            o The College's image bank.

            o The CAD group's collection of computer models (already

            o The Doctoral Program's recent dissertation proposals and

            o Example archive of Kandinsky paintings.

            o Images of 3D CAD projects.

      The principal media type in ArchiGopher is image.  Files are
      stored in both TIFF and GIF format.

   Vatican Library Exhibit

      In January 1993, the US Library of Congress mounted an electronic
      version of the exhibition ROME REBORN:  THE VATICAN LIBRARY AND
      RENAISSANCE CULTURE.  The exhibition was subsequently processed by
      the University of Virginia Library. The text files were broken
      into individual captions associated directly with each image and a
      WAIS-searchable version of the object index generated.  This has
      been made available on Gopher by the University of Virginia

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      This project is particularly interesting, as it demonstrates some
      limitations of the Gopher system.  The principal media types are
      image and text, and it is difficult to associate a caption with
      its image - each must be fetched separately, and using the XMosaic
      or xgopher client software it is not possible to tell which menu
      entry is the image and which the caption. (This may be a
      consequence of how the data has been configured for the Gopher
      server; if so, a requirement for better publishing tools may be
      indicated.)  Furthermore, searching the object index will result
      in a Gopher menu containing references to catalogue entries for
      relevant exhibits, but not to the online images of the exhibits
      themselves, which severely limits the usefulness of the index.

      It is interesting to note that during the preparation of this
      report, the Vatican Exhibition has been mounted on the WorldWide
      Web (WWW).  The hypermedia presentation on the Web is very much
      more attractive to use than the Gopher version.


      Jukebox is a project supported by the EEC libraries program.  The
      project aims to evaluate a pilot service providing library users
      with on-line access to a database of digital sound recordings.
      The database will support multi-user access and use suitable
      storage media to make available sound recordings in a compressed
      format.  Users will access the service with a personal computer
      connected to a telematic network.

   Scientific Publishing

   There are several refereed electronic academic journals presently
   distributed on the Internet.  These tend to be text-only journals,
   and have not really addressed the issues of delivering and
   manipulating non-text data.

   Many scientific publishers have plans for electronic publishing of
   existing academic journals and conference proceedings, either on
   physical media or on the network.  The Journal of Biological
   Chemistry is now published on CD-ROM, for instance.  Some publishers
   view CD-ROM as an interim step to the ultimate goal of making
   journals available on-line on the Internet.

   The main types of non-text data which are envisaged are:

      o    Images.  In many cases, image data (a microphotograph, say)
           is central to an article.  Software which recognises that
           the text may be of secondary importance to the image is

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      o    Application-specific data.  The ChemLab and MoleculeLab
           applications are widely used, and the integration of
           corresponding data types with journal articles will enhance
           readers' ability to visualise molecular structures.
           Similarly, mathematics appearing in scientific papers could
           be represented in a form suitable for processing by
           applications such as Mathematica.  Mathematical content
           could then become a much more interactive and dynamic aspect
           of research publications.

      o    Tabular data.  The ability for a reader to extract tabular
           data from a research paper, to produce a graphical
           representation, to subset the data, and to further process
           it in a number of different ways, is viewed as an essential
           part of scientific electronic publishing.

      o    Movies.  The American Astronomical Society regularly
           publishes videos to go with its academic journals.
           Electronic publishing can improve on this "hard copy"
           publishing by integrating video data much more closely with
           the source article.

      o    Sound.  There is perhaps slightly less demand for audio
           information in scientific publishing, but the requirement
           does exist in particular specialities (such as acoustics and
           zoology journals).

   Access to academic journals using at least four different paradigms
   is envisaged.  Hierarchical access, perhaps using a traditional
   journal/volume/issue/article model, is perhaps the most obvious.
   Keyword searching (or full-text indexing) will be required.  Browsing
   is another useful and often underestimated access model - to support
   browsing it is essential that "eye-catching" data (unlikely to be
   textual) is prominently accessible. The final method of access is
   perhaps the most important - the use of interactive viewing tools.
   Such tools would enable navigation of hypermedia links within and
   between articles, with gateways to special-purpose applications as
   described above.  The use of these disparate access methods implies
   more than one structure being applied to the same underlying data.

   Standards, particularly SGML, are becoming important to publishers,
   and it is clear that the SGML-based HyTime standard will be a front
   runner in providing the kind of hypermedia facilities which are being
   envisaged.  However, progress towards a common SGML Document Type
   Definition (DTD) for scientific articles, even within individual
   publishing houses and for text-only documents, is slow.

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   A specific initiative involving interested parties will be required
   to formalise detailed requirements and to pilot standards in this
   area.  A preliminary demonstrator project, funded by publishers and
   by the British Library Research and Development Department, involves
   making about 30 sample scientific articles available over the
   SuperJANET network, using a range of different software products. The
   demonstrator project is being managed by IOP Publishing and is being
   carried out at Edinburgh University Computing Service.

   Existing tools, particularly WAIS and WWW, are relevant, but adequate
   security and charging mechanisms are required if commercial
   publishers are to use them.  Many research groups are now making the
   text of preprints and published research papers available on Gopher

   It is interesting to note that the proceedings of the Multimedia 93
   conference run by the ACM will be published electronically (on CD
   ROM), using a multimedia document format designed specifically for
   the event.

   Computer-aided Learning

   The ready availability of user-friendly multimedia authoring tools
   such as AuthorWare Professional, Asymmetrix Multimedia Toolbook,
   Macromind Director and many more, has stimulated much interest in
   multimedia for computer-aided learning applications within the user
   community.  Sophisticated interactive multimedia courseware
   applications are being developed in many disparate subjects
   throughout the European academic community.  Users are now beginning
   to ask network technologists, "how can I make my multimedia
   application available to others across the network?".

   There is considerable interest in using the network to enhance
   delivery of multimedia teaching materials - for instance to allow
   students to take courses remotely (distance learning) and for their
   learning process to be supported, monitored and assessed remotely.

   The requirements which flow from this type of network application
   include the ability to identify and authenticate the students using
   the material, to monitor their progress, and to supply on-line
   assessment exercises for the student to complete.  Multimedia
   authoring tools allow very attractive presentation environments to be
   created, which encourages learning; this is viewed as essential by
   course developers.  Easy-to-use authoring tools (preferably existing
   commercial ones) are also essential.

   Finally, some learning applications involve simulations - examples
   include meteorological modelling and economic simulations.  Network

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   delivery of teaching materials should cope with this requirement
   (perhaps by acknowledging that executable scripts are just another
   media type).

   General Information Services

   There are many other possible uses of multimedia data in networked
   information servers which don't conveniently fall into any of the
   above categories. Some examples are given below.

      o    On-line documentation.  Manuals and instruction books often
           rely heavily on pictorial information, and are enhanced by
           dynamic media types (sound, video).  The ability to access
           centrally-held manuals across a network makes it much easier
           to keep the information up-to-date.

      o    Campus-wide information systems (CWIS) are an important
           growth area.  The opportunities for enhancing such a
           service with multimedia data (e.g., maps) is obvious.

      o    Multimedia news bulletins (e.g., the Internet Talk Radio,
           which is sound only).

      o    Product information (the multimedia equivalent of paper
           advertising matter).

      o    Consumer systems - e.g., tourist information servers.  The
           utility of such systems in an academic/research environment
           is perhaps questionable, but it is likely that such systems
           will address problems which will also be met in this
           environment.  We should be prepared to learn from such

2.2. Data Characteristics

   Some of the characteristics which make data more appropriate for
   network publication rather than publication on physical media are
   listed below.

      o    The data may change frequently.

      o    Implementing corrections and improvements to the data is
           very much easier.

      o    It is more readily available to the data user - no
           purchase/delivery cycle need exist.

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      o    Publication on physical media may not be cost-effective for
           very large volumes of data.  (Of course, there is a cost in
           networking the data as well, but the research/academic user
           is normally insulated from this.)

      o    Access for large user communities can be established without
           requiring each user to purchase a potentially expensive
           physical media peripheral (such as a laser disk player).
           This is particularly helpful in classroom situations.

      o    It may require less effort from the data publisher to make
           data available over a network, rather than set up a manual
           mechanism for distributing physical media.

      o    If related data from many different sources is to be
           published, it may be more efficient to leave the data in
           situ, and simply publish the network addresses of the data.

   There are counter-reasons which may make physical media distribution
   more appropriate:

      o    Easier to charge for.  (However, charging mechanisms do
           exist in some network information systems.  It may be that
           potential information providers need to be made more aware
           of this.)

      o    Easier to deter or prevent copyright infringement, using
           traditional copy-protection techniques.

2.3. Requirements Definition

   From studying the applications described in the preceding section,
   and from discussions with the people involved with the applications,
   it is possible to draw up a list of general requirements which a
   distributed multimedia information system for the academic and
   research community should satisfy.  These requirements are informally
   described in the following subsections.  The descriptions are
   necessarily informal and incomplete: every individual application
   will have its own detailed requirements, which would take a great
   deal of effort to determine (and indeed some of the requirements may
   not become apparent until the application is into its development


   It is clear that the European academic community, in common with
   other such communities, requires support for three main platforms:
   UNIX, Apple Macintosh, and PC/Windows.  For multimedia client/server

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   systems, the latter two are less appropriate as server platforms, but
   client support for all three is vital.  UNIX will be most often used
   as the server platform.

   There are other systems, such as VAX/VMS, which are also important in
   some sectors.

   Media Types

   Unsurprisingly, all applications require text data to be supported as
   a basic media type.  Image and graphic media types are next in
   importance, followed by "application-specific" data (such as tabular
   scientific data, mathematical equations, chemical data types, etc).
   Sound and video media types are becoming more important as users
   discover how these can enhance applications.

   Many different encodings are possible for each media type (e.g.,
   image data can be encoded as TIFF, PCX, GIF, PICT and many more).  An
   information system should not constrain the type of encoding used,
   and should ideally offer either a range of alternative encodings, or
   conversion facilities between the stored encoding and an encoding
   suitable for display by the client workstation.


   It is clear that many applications require their users to be able to
   navigate through the information base according to relationships
   determined by the information provider - in other words, hyperlinks.
   Academic publishing, CAL, on-line documentation and CWIS systems all
   require this capability.  The user should be able, by some action
   such as clicking on a highlighted word in a text node or on a button,
   to cause another node or nodes to be retrieved and displayed.

   Some "hypermedia" systems are in fact simply hypertext, in that they
   require the source anchor of a hyperlink to be in a text node.  A
   true hypermedia system allows hyperlinks to have their source anchors
   in nodes of any media type.  This allows a user to click the mouse on
   a component of a diagram or on part of a video sequence to cause one
   or more related nodes to be retrieved and displayed.

   Some hypermedia systems allow target anchors of a hyperlinks to be
   finer-grained than a whole node - e.g., the target anchor could be a
   word or a paragraph within a text document.  Without such a
   capability, it is necessary for target nodes to be quite small if
   precision is required in a hyperlink.  This may be difficult to
   manage, and fine-grained target anchors are therefore better.

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   Additional structure above or orthogonal to the underlying
   hyperlinked data is required in some applications.  This allows the
   same (generally non-textual) data to be used in several different
   applications, or the implementation of different access paradigms.


   Related information of different media types must be capable of
   synchronised display.  Commercial multimedia authoring packages
   provide many different ways of presenting, synchronising and
   interacting with media elements.  Some of these are summarised below.

      o    Backdrops.  An application may present all its visual
           information against a single background bitmap - e.g.,
           a CAL application might use a background image of an open
           textbook, with graphics, text and video data all presented
           on the open pages of the book.

      o    Buttons.  A "button" can be defined as an explicitly-
           delimited area of the display, within which a mouse click
           will cause an action to occur.  Typically, the action will
           be (or can be modelled as) a hyperlink traversal.
           Applications use different styles of button - some may use
           "tabs" as in a notebook, or perhaps "bookmarks" in
           conjunction with the open textbook backdrop mentioned above.
           Others may use plain buttons in a style conforming to the
           conventions of the host platform, or may simply highlight a
           word or phrase in a text display to indicate it is "active".

      o    Synchronisation in space.  When two or more nodes are
           presented together (e.g., because a link with more than one
           target anchor has been traversed), the author of the
           hyperdocument may wish to specify that they be presented in
           a spatially-related way.  This may involve: x/y
           synchronisation - e.g., a video node being displayed
           immediately above its text caption; it may involve
           contextual synchronisation - e.g., an image being displayed in
           a specific location within a text node; or it may involve z-
           axis synchronisation as well - for instance a text node
           containing a simple title being displayed on top of an
           image, with the text background being transparent so that
           the image shows through.

      o    Synchronisation in time.  Isochronous data may require
           synchronisation - the obvious case being audio and video
           tracks (where these are held separately).  Other examples
           are: the synchronisation of an automatically-scrolling text
           panel to a video clip (for subtitling); or to an audio clip

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           (e.g., a translation); or synchronising an animation to an
           explanatory audio track.


   Database-type applications require varying degrees of sophistication
   in retrieval techniques.  For applications addressed in this report,
   non-text nodes form the major data of interest.  Such nodes have
   associated descriptions, which may be plain text, or may be
   structured into fields.  Users need to be able to search the
   descriptions, obtain a list of "hits", and select nodes from that
   list to display.  Searching requirements vary from simple keyword
   searching, via full-text indexing (with or without Boolean
   combinations of search words), to full SQL-style database retrieval


   The user must be able to annotate documents retrieved from the
   information server.  The annotations may be stored locally.
   Similarly, the user may wish to add his own (locally-held) hyperlinks
   to documents.  (Actual modification of documents in the information
   system itself, or shared annotations to documents - i.e., the
   information system as a CSCW environment - is viewed as separate
   issue which this report does not address.)

   If an information provider has included contact details (such as a
   mail address) in a document, it should be possible for the reader to
   invoke a program (such as a mailer) which initiates communication
   with the author.

   In some applications, it may make sense for a user to be able to
   specify a region of interest in an image or movie clip, and to
   request a more detailed view of (or other information about) that

   Some applications require a sequence of images to be presented under
   control of the user.  For instance, a three-dimensional microscopic
   structure could be represented as a sequence of images taken with the
   microscope focused on a different plane for each image.  For display,
   the user could control which image was displayed using some kind of
   slider control, giving the illusion of focusing a microscope.  (This
   particular example has been taken from the Theseus project at John
   Moore's University, Liverpool, GB.)

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   Quality of Service

   Research has shown [3] that user toleration of delay in computer
   systems depends on user perception of the nature of the requested
   action.  If the user believes that no computation is required,
   tolerable delays are of the order of 0.2s.  If the user believes the
   action he or she has requested the computer to perform is "difficult"
   - for instance a computation of some form - then a tolerable delay is
   of the order of 2s.  Users tend to give up waiting for a response
   after about 20s.  Networked multimedia information systems must be
   able to provide this level of responsiveness.


   In order to support applications involving real-money information
   services (e.g., academic publishing) and learning/assessment
   applications, there must be a reliable and secure access control
   mechanism.  A simple password is unlikely to suffice - Kerberos
   authentication procedures are a possibility.

   Users must be able to determine the charge for an item before
   retrieving it (assuming that pay-per-item will be a common paradigm
   alternatives such as pay-per-call, pay-per-duration are also
   possible).  Access records must be kept by the information server for
   charging purposes.

   Learning applications have similar requirements, except that the
   purpose here is not to charge for information retrieved, but to
   monitor and perhaps assess a student's progress.


   Many authoring packages provide scripting languages.  In most cases,
   these languages are used to manage the presentation environment and
   control navigation within the hypermedia document.  There are other,
   declarative rather than procedural, methods for achieving this, so
   scripting of this type is not necessarily a requirement.  However,
   some application areas require executable scripts for other purposes
   (e.g., simulations in CAL applications).  Care in providing such a
   facility is required, because of the potential for abuse (the
   possibility of "trojan" scripts).  However, there is work going on to
   produce "safe" scripting languages - an example is "safe tcl", being
   developed by Borenstein and Ousterhout (contact

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   Bytestream Format

   For the easy transfer and handling of a hyperdocument, it must be
   capable of being encoded into a bytestream form, in such a way that
   the structure of the document is preserved and it can be decoded
   without loss of information.

   This facility makes it possible for such documents to be supplied to
   a user over electronic mail, in such a way that he or she can browse
   them at his or her own site.  This may be appropriate where the user
   does not have a direct connection to the Internet.  It will also be
   useful for printing the hyperdocument.


   It is essential that a multimedia information system should have
   adequate authoring tools which make it easy to prepare and publish
   hypermedia information.  Such tools need similar power to existing
   commercial multimedia authoring software for stand-alone multimedia

(page 24 continued on part 2)

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