Opengeo: an open geometric knowledge base. OpenGeo is an enhanced version of the geometric knowledge base developed by Chen, Huang, and Wang, which is equipped with web-based interfaces and new management facilities and made open and online. The kernel of the knowledge base consists of typical geometric knowledge objects such as definitions, theorems, and proofs. Several tools have been developed to support users to manage the knowledge objects contained in OpenGeo. Users can create new knowledge objects and add them to OpenGeo.