The AA (Academy of Athens) is co-chairing the Thesaurus Maintenance WG aiming at designing and establishing an overarching thesaurus for the humanities, a model on how existing thesauri and ontologies can be made interoperable and maintained in a sustainable way. The work of the WG focused on identifying top-level-concepts (facets and hierarchies) that became its common methodological basis, meeting the demands for objectivity and interdisciplinarity. Our work enables collaboration, cross-disciplinary resource discovery, and detection of common principles and ensures compatibility with other thesauri that are restricted to areas of knowledge. AA with its expertise in building specialist thesauri in most to the Arts and Humanities fields provided the terminology to support the bottom-up method used to define the intellectual principles on which is based the methodology of the Backbone Thesaurus model. Furthermore AA is responsible for coordinating the social collaboration (workflows and decision procedures) of the WG.