This book presents technical knowledge already available and identifies operational-methodological flows aimed at filling the existing incomplete and jumbled procedures through the use of parametric and virtual digital models for architectural heritage. Specifically, it proposes a digital code of practice for the conservation and management of existing architectural heritage through the aid of CityGML-Based models implemented with a Technical Decision Support System (T-DSS), as well as through expeditious VR-based approaches. It discusses the analysis of the methodological and technical principles for the development of semantic information systems for the study, modelling, cataloguing, and technical management of architectural heritage in a digital environment.