need to be investigated as well as the options
by which they need to be accessed by the
students.
Scanners are available to capture images from
photographs, slides or videotape frames.
Scanning technology has yielded an increase
in the format (A to E size), type (flatbed and
drum), gray level value (0 to 255), and
resolution (75 to 1000 dots per inch) that can
be obtained from commercially available
scanners. The common output from a scanner
is a file that contains one or three bands of
digital data that represent the image being
scanned. This file is a two-dimensional array
made up of pixels (picture elements), each of
which has a recorded spectral value between
0 and 255 in each of one to three bands.
Images from videotape and still video
cameras that generate a National Television
Systems Committee (NTSC) standard signal
can also be grabbed using an appropriate
frame grabber and image processing
software. Software is available to convert
these images to that they can be displayed on
a microcomputer or workstation. Finally,
Hypercard or external commands can display
the images at appropriate windows during the
interaction between the user and the
hypermedia system.
The final phases of system design is testing
and evaluation. Testing should involve
frequent checks during the design and
development of the hypermedia information
base for such things as navigation and use of
stacks, buttons, text fields, visual effects,
and sound. Once the network has been
constructed, one must trace all its paths to
verify that it actually captures the
relationships among all of its objects.
Depending upon its completeness and
accuracy, it may be necessary to refine the
stack structure or even repeat the process one
or more times to obtain an exact model.
Evaluation can take place by watching and
listening to testers and reviewers carefully.
The stacks should also be checked on all
intended machines with all possible memory
configurations.
HYPERMEDIA AND EXPERT SYSTEMS
The marriage of multimedia and expert
systems is inevitable for two important
reasons: (1) hypermedia can provide context
sensitive help for expert systems, and (2)
hypermedia can be used as the initial step for
conceptualization of the photointerpretation
knowledge which subsequently will be
represented in an expert system tool (Parsaye
et al, 1989; Shafer, 1990).
While, the ability to provide context-sensitive
help has become a standard in many
commercial applications software packages, it
is uncommon in most expert systems
including expert interpretation systems
(Argialas and Narasimhan, 1988, Argialas
and Harlow, 1990). A hypermedia
information base is needed to assist the
novice analysts of expert photointerpretation
380
systems to understand those terms of the
knowledge base that are ambiguous or hard.
A hypermedia system may allow us to
communicate with an expert system more
effectively and efficiently. Representing key
terms within a hypermedia system can make
the expert system more intuitive to the users
and provide the foundation on which a more
comprehensive and less ambiguous
knowledge base can be built.
Incorporating photographic images in expert
systems through a hypermedia system may
serve to illustrate conditions that are too
complex for verbal explanation alone. The
student would have a visual aid to enable him
to understand the knowledge base
terminology and have a more consistent
approach to visualizing photointerpretation
objects and attributes. Definitions,
descriptions, diagrams and photographic
images may reduce the potential for
confusion and misinterpretation by relying on
the intrinsic perceptual intelligence of the user
and so tend to avoid misunderstandings that
could result if only descriptive text were
used. Hypermedia can be used to offer users
not only a single piece of explanatory text or
a visual aid but also a doorway into the entire
photointerpretation knowledge through links
active from that particular node.
Hypermedia can also be used to assist us in
the development of expert photo
interpretation systems. A photointerpretation
hypermedia system could help to outline the
photointerpretation knowledge base. While
hypermedia by itself is not capable of creating
intelligent applications, it can help to delineate
the overall photointerpretation-related domain
by revealing how certain components or
objects are related to each other and to the
clues for their recognition.
Building a hypermedia information base
could help us, relying on our own natural
intelligence, to acquire, conceptualize,
organize, structure and represent the structure
of photointerpretation knowledge in a
semantic network which consequently can be
implemented in an expert system formalism.
Using hypermedia in this capacity it may also
reveal the highly complementary nature of
hypermedia and expert system technologies.
AN OUTLOOK
A photointerpretation hypermedia system will
allow students to interactively and non-
sequentially locate, browse, and learn
photointerpretation concepts and processes.
To the degree that the photointerpretation
hypermedia system will emphasize the
relationship between concepts and ideas
instead of words, it might make
photointerpretation easier to learn. The
associations provided by links in the
hypermedia system will facilitate
remembering relationships between ideas,
concept formation, and understanding. The
greater sense of control over the reading
process may produce involvement and desire