The conservation of existing architectural heritage requires a multi-level and multi-thematic approach for analysis and diagnosis, capable of systematically collecting and correlating architectural (buildings, churches) and urban elements (streets, open spaces), along with building components (walls, roofs) and service infrastructures (water, electrical networks). This process must comply with landscape regulations and support the prioritisation and coordination of intervention strategies. Traditional tools and procedures for developing recovery plans often reveal critical limitations in data interpretation, integration, and time efficiency. Conversely, recent advancements in IoT and digital technologies demonstrate that structured ontologies (e.g. CityGML, IFC) and information systems (e.g. geo-databases, relational databases) facilitate the organisation of technical knowledge and the definition of consistent relationships aligned with current regulatory frameworks. In this context, the proposed book aims to systematise existing technical information while addressing fragmented and inefficient procedures through parametric and virtual digital models. The book introduces a digital code of practice for the conservation and management of architectural heritage, utilising CityGML-based models integrated with a Technical Decision Support System (T-DSS) and streamlined VR-based tools. The approach begins with an analysis of methodological and technical principles for developing semantic information systems dedicated to the digital study, modelling, cataloguing, and management of built heritage.