The present article is focused on the genesis analysis of the Knowledge Building model (KB), to describe its actual formulation and to identify possible further developments. We will consider, first of all, from the socio-cultural scenario of reference, theoretical themes that are autonomous areas of research in the work of Bereiter and Scardamalia, but producing relevant ideas included the KB model. We mean the distinction between the two different approaches in writing called by the authors “Knowledge Telling” e “Knowledge Transforming” and the technique defined “procedural facilitation”. We define then the KB model through its principles and we describe the evolution of supporting technology (from CSILE to Knowledge Forum). We identify, finally, in connection with other models of community, new directions of inquiry that can contribute to a further development of the model.