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5. FULL-FLEDGED METHODOLOGIESAs soon as softwarehouses working in the area of conventional software development sensed the commercial uptake of expert systems, they entered the market by profiling themselves as competitors through their methodologies. These were mostly the same they also used for developing conventional systems, with an added "KBS-specific" component, mostly focused on knowledge acquisition and representation. As their methodologies were full-fledged, in the sense that they covered all levels of the pyramid and were of a broad scope, they automatically possessed a KBS methodology. As most of them were to a greater or lesser extent of the waterfall type described in Section 3, they shared the world view underlying this approach, though they differed in theories and methods6. In particular in Europe, these methodologies were seen to be proprietary to a company and the KBS methodology carried the name of the original with some kind of "AI," "KBS" or "Expert Systems"-like extension to it. In including KBS-specific elements, they relied heavily on advances made in R&D in the focused approaches described in Section 4. Some companies even started subsidiaries in the AI market, but most of these have disappeared by now. In general, for most softwarehouses, it turned out to be difficult to dress up in new clothes, a situation aggravated by the lack of qualified personnel because knowledge acquisition called for different skills than those possessed by most computer scientists and programmers. It can be safely stated that from this area not much new was added to the KBS development process not already known or developed elsewhere. From that angle, the short-lived nature of these methodologies is not surprising. In the wake of the disappointment with KBS benefits that overtook the initial optimism in the early 90s, building a KBS is just a particular brand of systems development in general, which occasionally occurs when things cannot be solved with conventional techniques. Thus, the need for profiling through proprietary KBS specific methodologies gradually faded away.
Of the full-fledged methodologies only a few are entirely KBS specific. The most complete and best known is the CommonKADS methodology, the product of two consecutive R&D projects funded by the European Community under the ESPRIT program. This is not the place to elaborate extensively this wide ranging methodology. The reader is referred to Schreiber et al. (1994) for a concise overview. Apart from being full-fledged, the interesting point in CommonKADS is its farewell to waterfall like approaches, and opting instead for a fully objectives and risk driven development approach, which owes much to the work of Boehm. Thus, the methodology also includes its own peculiar project management approach. To give its flavor, the CommonKADS worldview is summarized below:
The theory layer of the pyramid is embodied in the six models and their templates making up the CommonKADS model suite. These models are:
In addition, there are several libraries that can be used by the developer to shortcut the work. These also promote reuse over projects. The CommonKADS Workbench marketed by ISL from the U.K. is the powerful, though somewhat erratic, embodiment of the tools layer. Figure 4 shows the control window for the CommonKADS Workbench.
Figure 4 shows the four main aspects that play a role in the methodology:
Not shown is the Library which can be accessed from the "Guidance" menu item. CommonKADS is the sequel to KADS, which was wholly developed in the eighties. Therefore many ideas originated in KADS are incorporated in the focused approaches and the full-fledged methodologies which KBS specific grafts. In particular the library of generic expertise tasks as can be found in Breuker et al. (1988) and elaborated in Breuker and van de Velde (1994), has been frequently (re)used. It could be that this library is ultimately the most frequently used product of the entire KADS endeavor. The COMMET methodology (Steels, 1990; 1993) has not been widely published. It is based on the theory that three major components make up a knowledge level description of expertise: the model perspective, the task perspective, and the method perspective. These perspectives are refined in a "spiral" movement. The COMMET approach is supported by a workbench described in Steels (1993). However, the move to operational use has been mainly limited to Belgium and there was never a commercially available version of the COMMET workbench. Though not sailing under the flag of a methodology, the book by Prerau (1990) comes fairly close to the methodology definition of Section 2. Though the world view is not stated explicitly, the sequence of phases that Prerau describes is of the familiar waterfall type. But the support for carrying out these phases as presented in the majority of the chapters is, most of the time, very KBS specific.
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