This contribution proposes an ontology that arises from work on the Stemmarest text tradition repository, carried out as part of the SNSF project "The Chronicle of Matthew of Edessa Online". We describe the definitions, relationships, and assumptions that have been made in the process of producing a functional piece of software whose primary object is to collect and manipulate data in order to produce a critical edition of variant text. Our purpose is twofold: first, to offer a resource (or at least a starting point) for those who would develop software for text critical edition; second, as a practical experiment, to explore where our data model tests the limits of ontological reasoning.