The CoVHer Erasmus+ project addresses the long-standing lack of standardisation in hypothetical virtual 3D reconstruction and modelling in architectural heritage research. It aims to develop best practices for the 3D reconstruction of lost or never-built architectural heritage, enhancing research quality, transparency, and reusability. The collaborative effort includes contributions from five European universities and two private companies, focusing on architecture, archaeology, digital humanities, and art history. The presented workflow of documentation is the result of the joint effort in extensions of the approaches of the Scientific Reference Model (SRM) and Critical Digital Model (CDM), which strive for faithful reconstruction, documenting all decisions and inferences and advocate open licensing and use of non-proprietary formats to promote accessibility and reusability. The developed methodology aims to provide tools for the scientific evaluation of hypothetical reconstructions and support data exchange between researchers.

Highlights: The article describes the concept of a Scientific Reference Model (SRM) and its specific workflow and guidelines exemplified for a hypothetical 3D reconstruction of architectural cultural heritage. The article gives new insights and questions concerning the former synagogue in Ashmyany (Belarus) as a Case Study for testing the SRM concept. The article gives an insight into the market for infrastructures for publication and preservation of 3D models of cultural heritage using the example of the presented case study. This article examines the application of the Scientific Reference Model (SRM) concept in hypothetical three-dimensional (3D) reconstructions of architectural heritage, focusing on the synagogue in Ashmyany, Belarus. The SRM approach, tested in courses at the Hochschule Mainz, allows for transparent documentation of digital reconstructions to support further scholarly research and community engagement. Using historical source material, the 3D model of the synagogue in Ashmyany, serves as a case study for testing this methodology. The reconstruction process highlights the complexity of preserving Jewish architectural heritage in East Central Europe, where shifting political borders and a lack of comprehensive documentation complicate efforts. The synagogue’s architecture, including significant elements such as the Bima and Torah ark, was modelled using Building Information Modelling (BIM)-compliant software. However, certain elements had to be approximated due to limited historical sources, illustrating the challenge of reconstructing lost heritage with accuracy. The integration of historical photographs and surveys into the modelling phase not only enriched the digital reconstruction but also led to further questions about the building’s history and modifications over time. In addition to creating 3D models, the SRM emphasizes the importance of detailed documentation, following the FAIR principles to ensure that reconstructions are traceable and reusable for future research. Platforms like the CoVHer Repository facilitate the publication and accessibility of these models, alongside their metadata and source documentation. The Ashmyany synagogue case study demonstrates how 3D reconstructions can help visualize lost architectural heritage, offering new insights into its historical context and emphasizing the need for continued research on open repositories and digital preservation efforts. This approach showcases the potential of HBIM-modelling to contribute to the study and preservation of Jewish architectural heritage, while underscoring the ongoing need for community engagement and scholarly collaboration.

This work addresses issues related to digital 3D models of cultural heritage in the context of FAIR data. It introduces OntPreHer3D, an ontological extension of the CIDOC CRM for the comprehensive preservation of 3D models. OntPreHer3D semantically maps the intricate relationships between 3D models, their components, and their real-world equivalents. Through specialised classes and properties, it provides a robust framework for documenting diverse 3D models, including digitised objects, hypothetical reconstructions of lost heritage, and visualisations of never-built architectural projects. The paper highlights various documentation challenges and scenarios, underscoring the crucial need for data protection and the ability to re-model content in case of loss of the original 3D data. The presented ontology is rooted in the application ontology OntSciDoc3D, developed by the Institute of Architecture at Mainz University of Applied Sciences (AI MAINZ), for the scientific documentation of hypothetical 3D digital reconstructions. This further development included assessing the current limitations of the OntSciDoc3D, and official extensions of the CIDOC CRM family in the context of documenting 3D models. Crucially, given the inherent interpretative nature of hypothetical reconstructions, the presented framework integrates Inference to the Best Explanation (IBE) to transparently capture the human reasoning, choices, and uncertainties driving reconstruction decisions. It facilitates the semantic documentation of not only what was modelled, but also why and how confident we are in the interpretation, including the systematic quantification of uncertainty. Finally, the paper briefly presents results of a case study of the hypothetical reconstruction of the ruins of the Synagogue in Speyer (Germany) conducted by four different modellers equipped with the same source package, and predefined granularity and scope of the research. The study empirically examines how varying technical decisions made at the 3D software level impact the final models, demonstrating the critical role of such detailed process documentation in ensuring the long-term preservation and future reusability of 3D cultural heritage content.

Scientific practice relies on the rigorous documentation of procedures, methods, and outcomes, governed by principles like method verification, objectivity, and source disclosure. In the computer-based hypothetical 3D reconstruction of destroyed or never realised art and architecture, adhering to these principles faces challenges due to evolving software, methods, and data types, leading to a lack of standardised documentation and publication practices for 3D models. Consequently, the traceability, accessibility, and sustainability of research outcomes are compromised. Decades after the advent of computer-aided 3D visualisation in cultural heritage, there is a critical need to define applicable methodology and comprehensive documentation standards. Web-based platforms necessitate technical infrastructures and clear scientific methodologies to ensure understandable model creation and sustainable accessibility to 3D research data. The Scientific Reference Model proposes an accessible academic framework for this kind of 3D reconstruction, aiming to facilitate broad adoption. Developed and tested in research projects and educational contexts, this model aims to establish clear, accessible 3D models on the web, serving as foundational references for future research and knowledge dissemination.