Acquiring, elucidating and conceptualizing
such knowledge is the central task in building
intelligent systems. Intelligent
conceptualization is intellectually hard work,
and it best comes about through an
incremental and iterative process.
While this paper argues in support of
hypermedia, it is written in a linear,
sequential manner. It will be an erroneous
hypothesis to assume that the process of
decomposing knowledge takes place in a
series of successive steps. We, somehow,
are doing many steps in parallel, while their
implementation is normally taken place in a
serial manner. Hence, the actual process of
knowledge conceptualization is extremely
hard. .
IMPLEMENTING A HYPERMEDIA
SYSTEM
Once we have partitioned the specific
photointerpretation knowledge into a set of
nodes and links the next step is the
implementation of the information base in a
hypermedia system. À certain hypermedia
environment is selected and the sets of nodes
and links are formally represented and
programmed. Assuming that a Hypercard-
like system is selected, one needs to
determine the nature of the stack(s) to be
designed. The previously designed partition
of the knowledge into selected nodes and
links together with the need for easy and
efficient navigation can help determine each
stacks's structure. Hypercard supports
single-frame, linear, tree, network, and
combination stack structures (HyperCard
Stack Design Guidelines, 1989). Given the
complexity of the photointerpretation
process, it is speculated that a network or
combination stack structure might be most
appropriate. A network stack structure is one
in which students can explore in many
different ways (e.g., visiting other cards or
stacks). Navigation in network stacks may
be by reference points (or hubs), stack maps
or menus.
Depending on the specific subject matter one
may choose to include various levels of
image interpretation tasks for the most
significant aspects of general
photointerpretation in one stack. Additional
stacks may be required for advanced
interpretation tasks and for specialized tasks,
such as interpretation of specific geologic
formations or specific tree species.
Hypermedia systems permit and encourage
one to build a system incrementally, creating
new nodes/concepts and links as desired, one
at a time. Indeed, building a hypermedia
system is a cyclic, repetitive process. It is
likely that the design of the stacks, cards,
fields, buttons, etc will change significantly
in the beginning. One approach that could
help to cope with this iterative process is to
think of several solutions, design all of them
to a certain point, and then choose one for
further development.
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Some general guidelines for good stack
design are outlined in the following
(HyperCard Stack Design Guidelines, 1989).
The system should exhibit a well organized,
orderly, and well structured arrangement of
cards, fields, graphics, and buttons so that
students will be quickly able to learn,
understand, and use the system structure, the
most basic commands and the navigation
options to locate needed information
(Nielsen, 1990). The hypermedia cards can
include as much text or graphical elements as
appropriate, but screen-sized chunks of
information should be mostly used because
attaching more lengthy information to a
hypermedia node that must be scrolled
through on successive screens can be
disorienting to the student.
The hypermedia design should take
advantage of the hypermedia functions of the
selected authoring software system. It should
put information in obvious and intuitive
patterns so students can more easily locate,
browse, and understand the
photointerpretation knowledge. Good links
should relate concepts (not words), provide
minimum keystroke access to these concepts,
and help students to see the relationships
between concepts.
Card and background layouts should be
consistent for related cards. Navigation
buttons should be on every card, grouped by
function, and in the same place throughout
the stack perhaps on the edges of the screen.
The overall design should help the student to
control the navigation. The students student
should be able to find a certain piece of
information quickly or soon discover that it is
not in the information base within a minimum
number of keystrokes. The stack's
navigation must make use of menus, maps,
textual reminders, you-are-here indicators,
travel buttons, and progress indicators. The
stack should also have a title card, a proper
introduction describing the stack's purpose
and organization including the stack's size
and general layout, the stack's rules, and
their options. Topical menus, tables of
contents, and alphabetical listings should be
explained. A button of "Help" or "How to
use this stack" should be included on all
cards. The system should also offer context-
sensitive help.
The photointerpretation hypermedia system
should include a great number of aerial,
oblique, and ground photos as well as a lot
of illustrative diagrams such as cross
sections, profiles, and block diagrams. The
stimulus for seeking to include diagrams and
photographs comes from the inherent
complexity of the photointerpretation
process. Incorporating photographic images
will serve to illustrate conditions that are too
complex for verbal explanation alone. The
photographic images reduce the potential for
confusion and misinterpretation by
illustrating objects and conditions that might
be misunderstood if only descriptive text
were used. All potential uses of photos