Hypermedia is a computer-based information retrieval system that allows non-linear access to multimedia content such as text, audio, video, images and graphics through hyperlinks. It was created by Ted Nelson and contrasts with multimedia which refers to linear presentations without interactivity. The World Wide Web is an example of hypermedia, while a movie is an example of standard multimedia. Hypermedia development tools include programming languages and multimedia authoring software. Limitations of current hypermedia systems include user disorientation, high cognitive overhead and difficulty applying general systems to specific tasks. The basic hypermedia model consists of nodes connected by directed links to form a graph structure, with navigation between nodes through link activation.

1. HYPERMEDIA
• Hypermedia is a computer-based information
retrieval system that enables a user to gain or
provide access to texts, audio and video
recordings, photographs and computer graphics
related to a particular subject.
• Hypermedia is a term created by Ted
Nelson. Hypermedia is used as a logical extension
of the termhypertext in which
graphics, audio, video, plain text
and hyperlinks intertwine to create a generally
non-linear medium of information.

2. • This contrasts with the broader
term multimedia, which may be used to describe
non-interactive linear presentations as well as
hypermedia. It is also related to the field
of Electronic literature. The term was first used in
a 1965 article by Ted Nelson.[1]
• The World Wide Web is a classic example of
hypermedia, whereas a non-
interactive cinema presentation is an example of
standard multimedia due to the absence of
hyperlinks.

3. HYPERMEDIA DEVELOPMENT TOOLS
• Hypermedia may be developed a number of ways.
• Any programming tool can be used to write programs that
link data from internal variables and nodes for external
data files.
• Multimedia development software such as Adobe
Flash, Adobe Director, Macromedia Authorware, and
MatchWare Mediator may be used to create stand-alone
hypermedia applications, with emphasis on entertainment
content.
• Some database software such as Visual
FoxPro and FileMaker Developer may be used to develop
stand-alone hypermedia applications, with emphasis on
educational and business content management.

4. HYPERMEDIA -
LIMITATIONS, PROBLEMS
• While hypermedia has become more popular
and hypermedia systems come into more
widespread use, limitations and shortcomings
of current hypermedia are becoming
increasingly apparent (Halasz, 1988).
• The simple basic hypermedia model is not rich
enough to support the organising, structuring
and accessing tasks required by many
applications (Hammond, 1993).

5. • Problems like user Disorientation, development
of userCognitive Overhead and manual
construction of information network dominate
current hypermedia systems
(Ramaiah, 1992). Hypermedia Problems are
interrelated (Charles, 1993).
• For example when users are disoriented the
development of high cognitive overhead is very
possible. Additionally, applicability of general
purpose hypermedia systems to specific tasks is
problematic for casual non programmer users.

6. Hypermedia - Basic Hypermedia
Model
• Virtually, all hypermedia systems are founded in basic
hypermedia model. Likewise, a large part of current
hypermedia research assumes the underlying existence
of this basic model (Rivlin et all, 1994).
• Thus, it would be useful if we define the basic
hypermedia model. We can divide basic hypermedia
model in two distinguished but interdependent
submodels.
• The first one is the data submodel. According to this
submodel Nodes are interconnected with
directed Links forming the structure of a directed graph
(Parunak, 1991).

7. • Addition, deletion, update of nodes, links are
valid operations. Process submodel is the
second element of basic hypermedia model.
• This submodel concerns the information
access mechanisms of information
network. Figure 2 shows the data and process
submodels of basic hypermedia model.

8. • This model is foremost characterised by its
generality, flexibility and incompleteness. For example, E.F
Codd in his ACM Turing award lecture (Codd, 1981) defines
a data model as a combination of a data
structure, operations and integrity rules.
• In this sense, hypermedia data model is incomplete, since
it does not define any constraints (e.g. is valid the insertion
of a link without associate it to a destination node, see
Gronbajek et all, 1994) for determining the consistency of
information network.
• On the other side, process submodel is very
primitive, without using detailed specifications for defining
navigation access (e.g, how a user activates a link ).

9. Hypermedia - Data Submodel
• Nodes are the primitive unit for organising information in hypermedia network.
Nodes function as collections of primitive unstructured data which are bind
together in order to create one logical entity.
• The purpose of this logical entity should be to provide a coherent information
abstraction to existing information space. For example, in a hypermedia system
about the Aristotle's life, a node can combine a text description, a sound
information, a graphics picture and a digital video about the Aristotle's
birthplace, Stagyra. Links are the other fundamental units of data submodel. Links
implement the directed interconnections between nodes. They are Anchored to a
departure node and provide the hypermedia user the ability to activate them and
move to the destination node. Links are associated with parts of departure nodes
rather than with the node as a whole. This is less frequently for associations
between links and destination nodes. A simple variation of this model can be
achieved, regarding links as undirected interconnections between nodes than
directed (Halasz, 1994). But, since most of hypermedia systems don't support bi-
directional links we can not assume undirected links as part of the basic
hypermedia model. Figure 1 shows a graphical representation of a simple
hypermedia information network consisting of five nodes and several directed
links between nodes.

10. Hypermedia - Process Submodel
• Hypermedia concept is not only organised multimedia data
interconnected with links.Navigation, whereby the user
moves through the hypermedia network by activating and
following links from one node to another, is another
defining feature of hypermedia (Nielsen, 1990B).
Navigation is the primary means to access information in
hypermedia network, composing the most essential aspect
of basic hypermedia process submodel. The basic
characteristic of navigational access is that users navigate
by self motivation without having any external navigational
aid. Some primary navigational functionality like the ability
to backtrack to previous visited node, or to move the very
first visited node, could be regarded as part of basic process
submodel.