3.3 Hyper-G
Hyper-G is a technically superior information server developed at the Technical University of Graz. The Hyper-G team calls its system "...the first "second generation", publicly available, networked hypermedia information system running over the Internet.." [Hyper-G Readme]. Hyper-G integrates hyperlinking, hierarchical structuring, sophisticated search, and access control facilities into one single system, and is interoperable with other network information tools like Gopher and WWW [And95]. Hyper-G has its own SGML text format, Hyper-G Text Format (HTF). When accessed by a web client, Hyper-G text documents are converted on-the-fly into HTML documents. Contrarily to most other hypermedia systems, most prominently WWW, Hyper-G stores its links not within documents, but in a separate link database: links are therefore not restricted to text documents, they can easily be followed backwards, and they are updated and deleted automatically when their destination moves or is deleted (no "dangling links"), they are also easily visualized graphically.
Hyper-G is being developed jointly by the Institute for Information Processing and Computer Supported New Media (IICM) of Graz University of Technology, Austria and the Institute for HyperMedia Systems (IHM) of JOANNEUM RESEARCH, Graz, Austria.
ftp://ftp.iicm.tu-graz.ac.at/pub/Hyper-G/Harmony
Hyper-G includes a line mode browser, a browser for Windows called Amadeus, and a browser for UNIX/X11 called Harmony. In the following we present Harmony to contrast Hyper-G's extended capabilities with web browsers like Netscape.
Hyper-G's information is structured hierarchically. Harmony supports hierarchical browsing in that Harmony's Session Manager displays the hierarchical information structure of Hyper-G data similar to a graphical file browser (figure I.15).
Figure I.15 Hyper-G Harmony Session Manager
Harmony provides sophisticated search capabilities. It supports both attribute (keyword, title, author, creation time, etc.) and content (full text) searches. Search results are presented as a ranked list. The scope of searches is user-definable, ranging from individual collections to all collections on all Hyper-G servers world-wide. Selecting a document or collection in the local map, in the search result list, or following a hyperlink, causes the location of the corresponding object to be automatically displayed in the collection browser, providing a powerful aid to orientation.
Harmony supports hyperlinks between arbitrary document types, including text, image, film, PostScript, and 3D models. Source and destination anchors can be defined interactively.
Harmony's Local Map (figure I.16) presents a dynamically generated graphical overview of the link relationships of a chosen document: incoming and outgoing hyperlinks are represented. Selecting an object towards the edge of the map and generating a new display offers another means of associative browsing. On the negative side, performance is still somewhat limited in that it took 2 hours (!!!) on a Silicon Graphics workstation to generate the local map displayed in figure I.16.
Figure I.16 Hyper-G Harmony Local Map with center "About Hyper-G"
The Information Landscape (figure I.17) is a three-dimensional graphical overview map of the collection structure. Users can "fly" over the hyperspace landscape looking for salient features, select interesting documents, etc.. This feature requires platform support for a 3D graphics package such as IrisGL, OpenGL or Mesa. It is currently only available for SGI, DEC Alpha, Solaris, Linux, and HPUX machines.
Figure I.17 Hyper-G Harmony Landscape
Figure I.18 Hyper-G Harmony Landscape, zoomed in virtual reality
Hyper-G supports multilinguality. Harmony's user interface adjusts dynamically to the language of first choice, documents available in multiple languages are selected in order of language preference, and searches are optionally language-dependent.
Figure I.19 Hyper-G Harmony Text Viewer
Documents in Harmony are displayed by separate viewer processes in their own windows:
- Text
- A generic SGML parser is used to display Hyper-G (HTF) and WWW (HTML) texts. Inline images in GIF, JPEG, XPM, XBM and TIFF formats are supported (figure I.19).
- Images
- GIF, JPEG, and TIFF images are supported and may be zoomed, panned, etc..
- Movies
- MPEG-1 video streams are supported. Options include live display while loading, double size display, alternative dithering methods, and gamma correction. After loading, selective portions of the film may be replayed, the frame rate altered, etc.
- Audio
- The Audio Player supports both the Network Audio System[3] (NAS) and local audio commands provided by the client system.
- PostScript
- PostScript files can be displayed page by page, zoomed, printed, etc.
- 3D Scenes
- 3D model descriptions are displayed and can be manipulated
or traversed in three dimensions. Hyperlinks are attached to objects in the
model. This feature requires platform support for a 3D graphics package such
as IrisGL, OpenGL or Mesa and is currently only available for UNIX clients on
SGI, DEC Alpha Solaris, Linux, and HPUX machines.
All native Harmony viewers support both activation and interactive definition of
incoming and outgoing hyperlinks. Harmony can also be configured to use external
programs to display any document types (but without linking capabilities).
As can be seen from this brief description, Hyper-G offers superior functionality compared to WWW and its browsers such as Netscape. Nevertheless, Hyper-G in its current implementation is still more of a research system than of a commercial information system to be used by 20 million barely computer-literate Internet users, although there is a growing number of Hyper-G servers in daily practical use all over the world. It remains to be seen in what form the advanced concepts pioneered by Hyper-G will find its way into the web and its browsers.
After this introduction into world-wide information servers such as WWW and Hyper-G we will now describe how those servers can be extended and modified to incorporate new features and be adapted to special needs. The next chapter introduces programming environments for building new navigation tools and mechanisms for the web.