Development of the Agroforestry Expert System
The process of developing knowledge-based expert systems is known as
knowledge engineering, and it includes several distinct steps. The methodologies
proposed by Harmon and King [12], Waterman [31], Weitzel and
Kerschberg [32], and others were followed to ensure that UNU-AES was
successfully developed. Typical phases of expert system development are:
1. Selection of an Appropriate Problem
2. Development of a Prototype System
3. Development of a Complete System
4. Evaluation of System
5. Integration of a System
6. Maintenance
Alley cropping was selected as the focus of this first effort in the application
of expert system technique to agroforestry because of the availability of
knowledge in forms appropriate to expert system construction, and because
of its potential applicability as an agroforestry practice in developing countries.
Waterman [31] suggests that within the development of a prototype
system, there are actually three prototype systems developed. The first is the
demonstration prototype, the purpose of which is to determine if the
approach ('proof of concept') is viable and system development is achievable.
The second prototype, known as the research prototype, displays
credible performance on the entire problem. In most cases, the system is
'fragile' in several areas due to incomplete testing and revision. The third is
the field prototype, the purpose of which is to display good performance
with adequate reliability on the overall system. This activity is achieved by
extensive testing in the user environment [31]. This stage of development
precedes the development of a complete system and is the current status of
UNU-AES.
In order to develop the system, the domain experts (Nair, assisted by
co-workers) and the knowledge engineers (Warkentin, Ruth, and Sprague,
assisted by co-workers) interacted continously. The activities performed for
the selection of the appropriate problem and the development of three
prototypes will be discussed in a later publication. (Readers are encouraged
to contact the first author for additional details.)