rfc1614.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.


RFC 1614        Network Access to Multimedia Information        May 1994


    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
                       type.

    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
   characteristics.

   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

      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
              started).

            o The Doctoral Program's recent dissertation proposals and
              abstracts.

            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
      Library.




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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

      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
           required.



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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
   servers.

   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