The evolution of Protégé: an environment for knowledge-based systems development

The Protégé project has come a long way since Mark Musen first built the Protégé metatool for knowledge-based systems in 1987. The original tool was a small application, aimed at building knowledge-acquisition tools for a few specialized programs in medical planning. From this initial tool, the Protégé system has evolved into a durable, extensible platform for knowledge-based systems development and research. The current version, Protégé-2000, can be run on a variety of platforms, supports customized user-interface extensions, incorporates the Open Knowledge Base Connectivity (OKBC) knowledge model, interacts with standard storage formats such as relational databases, XML, and RDF, and has been used by hundreds of individuals and research groups. In this paper, we follow the evolution of the Protégé project through 3 distinct re-implementations. We describe our overall methodology, our design decisions, and the lessons we have learned over the duration of the project.. We believe that our success is one of infrastructure: Protégé is a flexible, well-supported, and robust development environment. Using Protégé, developers and domain experts can easily build effective knowledge-based systems, and researchers can explore ideas in a variety of knowledge-based domains. 1. Motivation and Protégé Timeline The Protégé system is an environment for knowledge-based systems development that has been evolving for over a decade. Protégé began as a small application designed for a medical domain (protocolbased therapy planning), but has evolved into a much more general-purpose set of tools. More recently, Protégé has developed a world-wide community of users, who themselves are adding to Protégé’s capabilities, and directing its further evolution. The original goal of Protégé was to reduce the knowledge-acquisition bottleneck (Hayes-Roth, Waterman, & Lenat, 1983) by minimizing the role of the knowledge engineer in constructing knowledge bases. In order to do this, Musen posited that knowledge-acquisition proceeds in well-defined stages and that knowledge acquired in one stage could be used to generate and customize knowledgeacquisition tools for subsequent stages (Musen, 1989a; b). Thus, the original version of the Protégé software (hereafter referred to as Protégé-I) was an application that took advantage of structured information to simplify the knowledge-acquisition process. Musen described Protégé-I as follows: Protégé is neither an expert system itself nor a program that builds expert systems directly; instead, Protégé is a tool that helps users build other tools that are custom-tailored to assist with knowledge-acquisition for expert systems in specific application areas. (Musen, 1989a, p. 2) Protégé-I demonstrated the viability of this approach, and of the use of task-specific knowledge to generate and customize knowledge-acquisition tools. However, it was custom-tailored to support a particular type of application. In particular, Protégé-I grew out of the Oncocin project and subsequent at-