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Requirements for Next-Generation Hypermedia Systems
Frank Halasz had originally identified seven issues for next generation
hypermedia systems.[Halasz, 1988]
Other researchers have come up with a few more over the past few years.[Lange, 1993], [Fountain et al., 1990]
Object-oriented database management systems seem to meet most of these requirements:
- Openness and Distribution
Most current hypertext systems are basically closed systems. That is, material
created in one system cannot be easily integrated with material created in
another system. An open hypermedia system is a system which can connect to
other information systems (both hypertext and non-hypertext). It should be
able to freely exchange data. Distribution allows the system to store at
geographically dispersed sites in a manner transparent to the user.
- Support for collaborative work or sharing
Future generation hypermedia systems must provide adequate support for
collaborative work. This includes simultaneous multi-user access to the
hypermedia network, robust concurrency control mechanisms, broadcasting to
users any changes made to the network by other users, and tracking
contributions made by each member of a team.
- Data integrity/Correctness
The database layer should preserve data integrity and provide traditional
secondary storage management and data administration facilities. It should
forbid dangling references to objects or attributes and prevent recursive
inclusion of composite objects.[Schutt & Streitz, 1990]
It should also support either the notion of rules as in extended relational databases or the
concept of semantics as in object-oriented databases.
- Dynamism
Most current generation hypermedia systems deal with static information.
Future systems need the ability to dynamically reconfigure the network in
response to changes made to the network or its contents. Virtual or dynamic
structures (active objects) are similar to dynamically generated views in
relational databases. Virtual structures are possible only when current
models are changed to adapt to changing information.
- Search and query mechanism
In addition to navigational access to information, hypermedia systems should
provide efficient search and query mechanisms. This would partly solve the
"lost in space" (disorientation) problem experienced by users during
navigation. There can be two kinds of queries - a structure query to retrieve
a part of the network and a content query to retrieve a specific node. The
former requires the development of a query language geared towards dealing with
hypertext network structures.
- Computation
The integration of AI into hypermedia engines will be an interesting area to
explore. This would include inheritance, truth maintenance, rule based
searching, and inference engines. Computation built into the hypermedia system
is likely to be more efficient for extensive access to information in the
network.
- Composites
With increasing use of hypermedia for sophisticated applications it becomes
necessary to deal with groups of nodes and links. This will require making a
composite node as a primitive construct in the basic hypermedia model.
Inclusion (or part-of) relations have to be supported in addition to standard,
referential links.
- Versioning
Versioning is required in order to keep track of changes to the network. This
can include versioning at the level of individual entities such as nodes and
links and also at the level of the hypermedia network as a whole.
- Multimedia Support
The database layer should be able to efficiently store and retrieve multiple
media. It should also provide transparent access to different storage media.
- Extensibility and Tailorability
Extensibility involves the ability to handle extensions to the existing data
model (schema evolution) in a flexible and safe manner. The database layer
should not only be able to handle the structural part of the hypertext data
model but also the semantic part to ensure data abstraction and encapsulation
of the evolving data model.
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