We describe an ontology for WWW summarization in Bone Marrow Transplantation that is currently under construction. It is text-based and qualifies as a grounded ontology. In addition, it is user-centered. For stating medical knowledge, we use first-order logic extended with contexts. The ontology is prepared to serve query scenario formulation, text passage retrieval and summarization proper in a summarization system. It will be stored and managed by an XML database server. Currently, our ontology is developed to the point that its features can be demonstrated.