The Essential Project tools have evolved over several years to address a variety of client needs and Essential is now the world's most popular open-source EA toolset. The tools of the Essential Project have been used for managing enterprise architectures in a large number of EAS client engagements and their usability and reliability have been tested and proven repeatedly in these engagements.   The Essential Architecture Manager repository tool is based on Protégé, a widely-used, open source knowledge base platform developed and maintained by Stanford University. Protégé has proved to be scalable, reliable and flexible for many years now.