You can check Hyper-G out at:
http://hyperg.tu-graz.ac.at/570F5164/A0x811be681_0x00071882
Francis
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Advancing the ideas of World-Wide-Web: Hyper-G
H. Maurer
Institute for Information Processing and
Computer Supported New Media,
Graz University of Technology, Graz/Austria
email: hmaurer@iicm.tu-graz.ac.at
Extended Abstract
WWW (World Wide Web)[Berners-Lee 92] has become the most
successful networked multimedia system employing the hypertext
paradigm over the last few years: Documents consisting of textual
information can have embedded pictures, movies or audioclips and reside
on a s e r v e r , accessible e.g. via internet using suitable v i e w e r
s. The
only structuring mechanism for sets of documents is the facility to place --
in hypertext fashion -- anchors in documents leading to (linking them to)
other documents. Although this mechanism can be used to create
menu-like hierarchical structures WWW databases are basically "flat"
(stratified) collections of documents linked together. Thus, a WWW
database can be seen as a graph whose nodes are the links between them.
WWW has become an easy to use tool, mainly for small and
medium-scale multimedia presentations that are accessible world-wide
due to the excellent M o s a i c - viewer that is available on all major
platforms: X-Windows, Mac and MS-Windows.
However, WWW has a number of limitations that become apparent once
tasks more complex than "a few hundred multimedia screen
applications" are considered. No full-text search is provided as part of the
WWW server, let alone the possibility to search across boundaries of
WWW servers; authorisation features are lacking, hence the installation
of a number of independent WWW servers within an organisation is not
uncommon, for the simple reason of preventing access of unauthorised
groups. This fragmentation prevents more global searches: thus, one of
the main aims - to tie information together - gets lost due to the lack of
authorisation features and the boundaries imposed by each WWW
server.
To overcome such weaknesses WWW offers an ingenious way out: it
allows to start arbitrary application programs, thus letting users link into
other databases, employ complex search algorithms or activate any other
program desirable on top of WWW servers. This great flexibility is
achieved, however, at a big cost: the uniformity of the interface
disappears, different WWW servers start to behave differently: the whole
"jungle" of scattered databases each with a different feel as we all know it
from Internet starts to reappear, now on the level of WWW.
Realizing this dilemma, a group of some 30 researchers and developers at
the Graz University of Technology has started to systematically examine
the ideas, structure and underlying features of large distributed
multimedia servers, leading, eventually, to a concept embracing WWW
yet more general than WWW: Hyper-G. Hyper-G has been developed
carefully to ensure cross-operability with WWW. Hyper-G databases have
gateways to WWW (and Gopher [Alberti 92]), and conversely; the Hyper-G
viewer A m a d e u s (for MS-Windows) and H a r m o n y (for
X-Windows) will allow the perusal of WWW databases; and the Mosaic
Viewers of WWW can be used to access Hyper-G servers. (For more
details on Hyper-G see [Andrews 94a], [Andrews 94b], [Hyper-G 94], [Kappe
93a], and [Kappe 93b].)
The main difference between WWW and Hyper-G servers is that Hyper-G
provides much functionality integrated into it (and hence uniform in
nature) that has to be implemented on top of WWW (and hence
potentially differs from site to site) and that Hyper-G servers work on a
truly distributed platform: a user can activate a number of Hyper-G
servers (that may or may not be arbitrarily geographically dispersed) in
such a fashion that the union of all the databases involved appears as if it
were one single database. Indeed, the Hyper-G concept is a bit deeper and
more general:
The basic item of a Hyper-G database is a document cluster rather than a
single document: this is a convenient tool to handle such diverse features
as multiple languages, multiple windows or multiple representations. A
typical example of the latter is the treatment of LaTeX documents in
WWW (Mosaic) and Hyper-G: in Hyper-G the basic idea is to store LaTeX
documents as a cluster of two documents: one of them is a textual
document with in-line pictures for all formulae (this is the approach
taken in WWW/Mosaic), the other document is the DVI File
corresponding to the LaTeX document containing links to e.g. pictures, i.e.
a file retaining all the precision and beauty of the original LaTeX version.
For casual browsing on a medium resolution screen the first alternative is
the only viable one, for serious viewing (or printing on a laser printer) the
second one (not available in WWW/Mosaic without some contortions) is
the only one that makes sense.
Document clusters in Hyper-G are put together in so-called c o l l e c t i o n
s, and a collection can be part of one (or more) parent collections. Thus,
Hyper-G structures its documents into a kind of hierarchy (actually not a
tree, but a DAG). This is useful for many reasons: documents can be
inserted without defining links (not possible in WWW: a document
without a link to it is not (properly) accessible in WWW; it is accessible in
Hyper-G, however, due to the collection structure); collections (and
document clusters) can have attributes, allowing Boolean searches on
those attributes; and although Hyper-G provides the full anchor-link
hypertext paradigm it also allows (Boolean or WAIS-like) full text
searches within the scope of any number of user-selected collections. Since
each Hyper-G database is a collection, users can activate even
geographically remote Hyper-G databases (better still: arbitrary
sub-collections within them) and perform powerful searches across all of
them.
Note that such a facility is rather hard to implement in WWW: although
full text search can be added on top of WWW databases, scope definitions
are very difficult and automatic searches across various WWW databases
are next to impossible. Thus, Hyper-G avoids the danger of independent
"WWW-empires", the "Balkanisation" of databases as Ted Nelson has so
aptly called it!
However, it must be clearly recognized that Hyper-G generalises, but
makes full use of WWW and Mosaic facilities.
It is worthwhile to look at a specific example. Suppose a university has
five different WWW servers operated by five different departments, each
department authorized to modify only its own database, and departments
unable or unwilling to combine the data for exaclty the mentioned
authorization problems. Although a good solution, it is not perfect: to
find information on person xxx within that university, each of the five
databases has to be queried. Maybe not even all of them support full text
searching or may support it using different mechanisms: thus, the
problem "where do I have to look and how do I do it" (well-known from
the world of Internet and international databases) can arise using WWW
even within a single institution (and even more so if the databases are
spread over various institutions). Using Hyper-G, each of the five
mentioned WWW databases can be converted into five Hyper-G
collections, all of them belonging to the collection "University yyy".
Authorisation to modify data remains where it is desirable, yet a single
full-text search for "Person xxx" in the collection "University yyy" will
reveal all information on person xxx, if any such information is available.
Observe that no manual changes in any of the WWW databases are
necessary; nor is it necessary to abandon the viewer Mosaic, if users have
started to like this beautiful piece of software. On the other hand, the
Harmony viewer (see below) does provide all of Mosaic's features and a
few additional ones (and is available free of charge like Mosaic), so may
become a welcome addition at some stage ...
To take a larger and maybe more pertinent example: suppose a number of
universities in Germany use Hyper-G, each with a collection
"Mathematics". By defining a collection "Mathematics in Germany" a
single search will examine all sub-collections "Mathematics"
automatically, independent of where they are located geographically.
We believe that above notion of unions of collections defining scopes for
searches (or other actions!) is essential to prevent that a new kind of
fragmentation occurring on a new level.
Hyper-G was developed using also knowledge of and experience with
WWW; Hyper-G is thus influenced by WWW and has systematically
tried to stay consistent with WWW without giving up the insights gained
in the meantime:
Big hypermedia systems must have a structure: a "flat" graph with
no "semantic" meaning of links will not do for large systems.
Activities in large networked multi-media systems have to be
restricted to scopes definable by the users.
- Activities that are considered central (like searching, structuring,
non-private annotations, etc.) have to be integrated into the basic
system so as to avoid unsystematic proliferation of
"unorthogonal" features.
Hyper-G is based on above premises.More on those and other points (like
mechnaisms for gathering statistics,billing and "active" mail )will be
contained in a full version of this paper. However, a few more specific
aspects should be mentioned:
The annotation concept in WWW (actually part of the Mosaic client)
allows "private" annotations that are stored locally. Hyper-G allows to
define authorisation classes for annotations, permitting "private",
"group" or "public" annotations.
Links in WWW are restricted to textual anchors, while Hyper-G supports
anchors in arbitrary data-types like pictures or movies. Links in Hyper-G
are bi-directional. Hyper-G introduces a sophisticated authorisation
mechanism defining for each user the rights to read, create links, modify
and annotate. This provides the basis for sophisticated customisation and
even CSCW within Hyper-G that have to be -- like all other more
sophisticated features -- built on top of WWW (potentially creating
confusion and incompatibility).
Hyper-G is being used as information system at a number of universities
(Graz University of Technology and the University of Auckland are two
examples); it has been selected as information system by major
organisations such as ESA (European Space Agency), it is the basis of a
multi-media guidance system by large museums or exhibition operators
(such as the new Museum of New Zealand, or the Images of Austria
Presentation at the EXPO' 92 at Sevilla); it is the platform of one of the
most ambitious (30 GByte data) multimedia projects anywhere (the
millenium celebration of Austria) and is the basis of the first serious
attempt of electronically publishing a high-quality journal in computer
scince, J.UCS (Journal of Universal Computer Science): J.UCS is suported
by Springer Pub.Co., has an editorial board of over 100 prominent
computer scientists and more than 25 universites world-wide have agreed
to act as server.
Hyper-G, as a late-comer in the field, has been able to profit from and
incorporate experience from earlier projects such as Gopher and WWW.
And despite the fact that Hyper-G will not be officially released before June
30, 94 above list does show a fairly wide acceptance even of its
pre-beta-release version.
Since Mosaic has been the main driving force for WWW it is worthwhile
to mention that the current X-Windows viewer of Hyper-G will be
replaced by Harmony. (The current Harmony version is available as
development prototype for functionality tests if specifically requested for
such tests; it must not be considered an operational tool before June 30, 94
[Hyper-G 94].)
Harmony includes all features of Mosaic, plus a graphical browser giving
document-type, history, in-and-out links, dynamic and static
environments, and incorporates a viewer of 3D objects and scenes
(including navigation within them) plus a first attempt at producing 3D
"information landscapes".
The MS-Windows Viewer A m a d e u s is available as of May 94. It
implements a subset of Harmony's features on a PC-Windows platform.
Summarizing, WWW has been successful in establishing networked
multimedia as a major option for information systems of the future.
Hyper-G has been built using experiences with WWW and other
large-scale networked multimedia systems, preserving full
interoperability with WWW, yet incorporating all those features into the
basic system that have been universally accepted as indispensable. In this
sense, Hyper-G tries to contribute to a more uniform and controlled
environment of the world opened by WWW.
References:
[Alberti92] Alberti B., Anklesaria F., Lindner P., McCahill M., Torrey D.,
"The Internet Gopher Protocol: A distributed Document Search and
Retrieval Protocol", Available by anonymous ftp from
boombox.micro.umn.edu in directory: pub/gopher/gopher_protocol.
[Andrews 94a] Andrews, K., Kappe, F.: Soaring Through Hyperspace: A
Snapshot of Hyper-G and its Harmony Client; Proc.
Eurographics-Multimedia 94, Graz, June 94; FTP iicm.tu-graz.ac.at in:
pub/Hyper-G/papers.
[Andrews 94b] Andrews, K., Kappe, F.: Hyper-G: A New Tool for
Distributed Hypermedia; submitted to ISMM Int. Conf. on Distributed
Multimedia Systems and Applications, Hawaii (1994); anonymous FTP
iicm.tu-graz.ac.at in: pub/Hyper-G/papers
[Berners-Lee 92] Berners-Lee T., Cailliau R., Groff J., Pollermann B.,
"WorldWideWeb: The Information Universe", Electronic Networking:
Research, Applications and Policy 1, 2 (1992), 52-58.
[Hyper-G 94] Reports, Information and SW concerning Hyper-G;
anonymous FTP iicm.tu-graz.ac.at in: pub/Hyper-G.
[Kappe 93a] Kappe, F., Maurer, H., Scherbakov, N.: Hyper-G -- A Universal
Hypermedia System; J.EMH (Journal of Educational Multimedia and
Hypermedia) 2, 1 (1993), 39-66
[Kappe 93b] Kappe, F., Maurer, H.: Hyper-G: A Large Universal
Hypermedia Systems and Some Spin-offs; anonymous FTP siggraph.org,
in: publications/May-93-online/Kappe.Maurer
Author: iicm
created: 94/09/28 15:40:25
modified: 94/10/24 16:39:35
Parent(s):
Research Papers on Hyper-G
________________________________________________________________________
Dr. Francis Heylighen, Systems Researcher fheyligh@vnet3.vub.ac.be
PESP, Free University of Brussels, Pleinlaan 2, B-1050 Brussels, Belgium
Tel +32-2-6292525; Fax +32-2-6292489; http://pespmc1.vub.ac.be/HEYL.html