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