CLIPS and COOL

~ ~ CLIPS is short for C Language Integrated Production System. It was developed for NASA by the Software Technology branch and the University of Georgia. CLIPS is detailed in [Giarratano 1991a], [Giarratano 1991b], [Giarratano 1991c], [Giarratano 1991d], and [Giarratano 1991e], and it was these references which made it possible to develop expert systems using CLIPS. CLIPS is available to the public and has several features which make it a desirable choice for producing the expert systems in SNEAKERS. It offers the ability to integrate expert systems developed in CLIPS into the environment of a standard C program. This allows for quick prototyping and testing of expert systems alongside the development of a control program written in C.

Since Motif was chosen as the user-interface development method, the ability to integrate CLIPS and Motif was a great benefit. In [Liu 1991], it is shown that CLIPS and Motif can be effectively integrated to form a useful and intelligent interface to a program which determines how tunnels should be made.

CLIPS version 5.0 was used, which introduces objects and object-oriented techniques, via COOL - CLIPS Object Oriented Language. These objects can be built into a part hierarchy which describes the parts of a tower. Towers are a part of the domain as discussed in chapter . These objects can be accessed by both a regular C program and the CLIPS expert systems. By using this part of the CLIPS package, a database was developed which contains knowledge about the domain, and knowledge about the relationships between the parts in the design. It is also possible to attach daemons to the objects. These daemons are programs which run whenever a specified action happens to an object. These programs can produce facts and transfer knowledge to appropriate agents as needed.

In the implementation of SNEAKERS, there is a common fact list that is controlled by CLIPS, which allows all knowledge to be seen by the separate agents. The fact list also allows the agents to communicate with each other by posting to the fact-list. The Critic posts criticisms to the fact-list, while the Suggestor reads these and adds suggestions to the list. Other agents can use the fact-list as a communication center as well. The benefit of this common fact-list is to overcome the problem of information routing which is mentioned in Section .

CLIPS also has the advantage of having an interpreted mode. This mode can be used for prototyping the agents before including them in the entire program. It is also useful for checking syntax and for trying several ideas about the way in which rules should be written. This feature was very useful for fast development of several agents simultaneously.

CLIPS was a very good choice for the expert building tool to use in conjunction with the other tools used. CLIPS is very robust and lends itself to inclusion in a variety of larger programs. The features listed above allow CLIPS to provide the required flexibility and power for developing the agents of SNEAKERS.