Knowledge representation of built heritage mapping an ad hoc data model in ocg standards: the case study of Pitti Palace in Florence, Italy

The description of a historic building can be made by considering many different aspects: stylistic, technological, formal, function-related, etc. In Architecture, as in any artistic form, intangible elements also play an essential role and are closely related to individual interpretation; therefore, achieving an objective description is challenging, and several efforts have been undertaken over time to reach the goal. Nested hierarchical or complex multi-dimensional relationship structures can be defined to represent various interrelationships between a huge variety of elements and their properties. Categorisation, standards definitions and adoptions, data modelling, etc., should come after the data collection phase to adequately support the sharing of disparate datasets and thus facilitate communication between experts in different domains and improve knowledge dissemination. The paper considers different approaches in the built heritage representation, then presents the ad hoc data model initially adopted in the Pitti Palace documentation project, where a comprehensive and highly detailed 3D digitisation project was recently carried out, and finally proposes to map it into widely adopted standard, such are CityGML and IndoorGML.