AI Magazine Volume 8 Number 2 (1987) (© AAAI) Knowledge Acquisition in the Development of a Large Expert System David S. Prerau nowledge acquisition is the domain for the expert system. The This article discusses several effective process by which expert sys- remaining points highlight techniques techniques for expert system knowledge tem developers find the knowl- for getting started in knowledge acqui- acquisition based on the techniques that edge that domain experts use sition, documenting the knowledge, were successfilly used to develop the Cen- to perform the task of interest. This and finally, actually acquiring and tral Office Maintenance Printout Analysis knowledge is then implemented to recording the knowledge. Each point and Suggestion System (COMPASS) form an expert system. The essential is followed by a general discussion and Knowledge acquisition is not a science, part of an expert system is its knowl- then by a description of how the point and expert system developers and experts edge, and therefore, knowledge acqui- must tailor their methodologies to fit their specifically applied to the COMPASS situation and the people involved. Devel- sition is probably the most important project. opers of future expert systems should find task in the development of an expert a description of proven knowledge-acquisi- system. tion techniques and an account of the In this article, several effective experience of the COMPASS project in techniques for expert system knowl- COMPASS applying these techniques to be useful in edge acquisition are discussed based developing their own knowledge-acquisi- on the techniques that were success- tion procedures fully used at GTE Laboratories to COMPASS is a multiparadigm expert develop the COMPASS expert system. system developed by GTE Laborato- Knowledge acquisition for expert sys- ries for telephone switching-system tem development is still a new field maintenance (Prerau et al. 1985b; and not (yet?) a science. Therefore, Goyal et al. 1985). COMPASS accepts expert system developers and the maintenance printouts from telephone experts they work with must tailor company central office switching their knowledge-acquisition method- equipment and suggests maintenance ologies to fit their own particular situ- actions to be performed. ation and the people involved. As In particular, COMPASS accepts expert system developers define their maintenance printout information from a GTE Number 2 Electronic own knowledge-acquisition proce- dures, they should find a description Automatic Exchange [No. 2 EAX). A of proven knowledge-acquisition tech- No. 2 EAX is a large, complex tele- niques and an account of the experi- phone call switching system (“switch”) that can interconnect up to ence of the COMPASS developers in 40,000 telephone lines. Such a switch applying these techniques to be use- ful. generates hundreds or thousands of The next section of this article is a maintenance messages daily. The cur- discussion of the COMPASS project. rent manual procedure of analyzing The major portion of the article fol- these messages to determine appropri- lows, with over SO points on knowl- ate maintenance actions takes a sig- nificant amount of time and requires a edge acquisition that were found to be high level of expertise. COMPASS important during the work on COM- uses expert techniques to analyze PASS. Initial points cover the knowl- edge-acquisition considerations in these messages and produce a priori- tized list of suggested maintenance selecting an expert and an appropriate actions for a switch-maintenance SUMMER 1987 43 technician. Selecting an Expert tics (rules of thumb). These heuristics COMPASS is implemented on most distinguish the knowledge in an A domain expert is the source of Xerox 1108 Lisp machines using the expert system from that in a conven- knowledge for the expert system. KEETMsystem (Fikes and Kehler 1985) tional program and are the main goal Therefore, even before the actual pro- from IntelliCorp. The COMPASS of the knowledge-acquisition process. cess of knowledge acquisition begins, implementation utilizes multiple arti- Our COMPASS expert, W. (Rick) ficial intelligence paradigms: rules, a decision crucial to its success must be made: the choice of the project’s Johnson, is a switching-services super- frame hierarchies, demon mecha- visor in the electronic operations staff nisms, object-oriented programming expert (or experts). Because of the sig- nificance of this decision, among the at General Telephone of the Southwest facilities, and Lisp code. important criteria for selecting an (GTSW). He has been working in tele- COMPASS is a large expert system: appropriate expert system domain are phone switching for 16 years, includ- the COMPASS “knowledge document” considerations related to the choice of ing about 5 years specifically on the (Prerau et al., 1986), which contains a No. 2 EAX. succinct English-language record of a domain expert. These considerations primarily relate to the degree that the l the COMPASS expert knowledge, is Select an expert who is capable of expert will function well in the role of communicating personal knowledge, approximately 200 pages long. The COMPASS implementation consists of knowledge source. judgment, and experience and the about 500 Lisp functions, 400 KEE methods used to apply these elements to the particular task. rules, and 1000 frames with a total of Importance of 15,000 slots. The system (COMPASS, An expert should not only have the Expert Selection expertise but also the ability to impart KEE, and Interlisp-D) requires about l Significant time and effort is needed this expertise to the project team, 10 megabytes. COMPASS alone to select an expert. whose members probably know little requires about 5 ,megabytes, and is The selection of an expert is an or nothing about the subject area. growing larger as data are analyzed. important element in knowledge In its initial field uses, COMPASS Experts should be introspective, able acquisition, and knowledge acquisi- to analyze their reasoning processes; has displayed performance comparable tion is critical to the overall expert and communicative, able to describe to (and, in some cases, better than) system. that of domain experts and significant- those reasoning processes clearly to Early in the COMPASS project, an the project team. ly better than that of average No. 2 extensive set of criteria for selecting EAX maintenance personnel (Prerau et The COMPASS expert was an excel- an expert system domain were devel- al., 1985a). COMPASS is probably one lent communicator in teaching the oped (Prerau 1985). This set included of the first major expert systems COMPASS knowledge engineering criteria for selecting a project expert designed to be transferred completely team the basics of the No. 2 EAX and (of these criteria, only those related to from its developers to a separate orga- in discussing and explaining the meth- knowledge acquisition are discussed nization for production use and main- ods he used to analyze No. 2 EAX here). We then spoke with several con- tenance. COMPASS has been put into maintenance messages. tacts in the domain area and explained extensive field use by GTE Data Ser- l our need for a project expert and our An expert should be cooperative. vices (GTEDS) of Tampa, Florida (Pre- criteria for selecting one. The discus- An expert should be eager to work rau et al., 1985d). It has been run on a sions yielded a small list of potential on the project or at worst be nonantag- daily basis for about a year to aid No. 2 EAX experts for our project. The onistic. It is a hard job to be a project maintenance personnel at 12 No. 2 most promising of these experts were expert and to have to examine in EAXs in four states. These switches asked to come separately to GTE Lab- detail the way you have been making service about 250,000 telephone sub- oratories for two days of meetings. At decisions. If the expert is not interest- scribers. COMPASS is currently being these meetings, we discussed the pro- ed or is even resentful about being on put into production use by GTE tele- ject, expert systems in general, and the the project, then the expert might not phone companies. potential participation of the expert in put in the full effort required. One way Because COMPASS is designed to be our project. At the same time, we tried to ensure a cooperative expert is to maintained by a group completely sep- to see how the potential expert met find a person who is interested in com- arate from its developers, major con- our selection criteria. Based on these puters and in learning about expert sideration during development was meetings, we selected the COMPASS systems (and possibly in becoming a given to the potential maintainability expert. local “expert” on expert systems and of the final COMPASS system. The AI when the project is completed). COMPASS project team developed a Also, an expert who sees a big poten- set of software engineering techniques An Expert’s Capabilities tial payoff in the expert system being for expert system implementation l Select an expert who has developed developed might want to be involved (Prerau et al., 1987). These techniques domain expertise by task performance with it. were utilized for COMPASS and are over a long period of time. The COMPASS expert was very being used in other expert system The expert must have enough expe- interested in, and enthusiastic about, developments. rience to be able to develop the the project, and the effort he put in domain insights that result in heuris- 44 AI MAGAZINE was more than what was expected. He Selecting the Domain task rather than the entire task at learned a good deal about AI and once. Combined with the previous expert systems during his work on the In addition to the selection of the item, the knowledge acquisition can COMPASS project and became famil- expert, criteria for the selection of an then be directed at any one time to one iar with the Lisp machines being used.