The construction industry relies on precise building information for evaluating designs performance, collaboration, and delivery. For more than a decade, the Level of Development (LOD) is the most popular concept for describing the progression of geometric and semantic information across the design phases. The LOD is a domain language that aims to establish a common understanding of what each level means to facilitate communication and defining deliverables in contracts among the project participants. However, multiple similar standards are published worldwide for a similar purpose, such as Level of Detail, Level of Definition, and Level of Information Need. However, although they are similar at first glance, in many cases, they have numerous deviations in their fundamentals. This paper investigates the differences of the LOD standards and their interpretation by the scientific community through a thorough analysis. For this purpose, 58 LOD guidelines were reviewed, and a systematic literature review of 299 peer-reviewed publications was conducted. As a result, existing trends in using the LOD in research and the most widespread LOD naming conventions and specifications were identified. Additionally, the results highlight 16 common use cases for applying the LOD.

The early stages of building design involve the consideration of different design variants and their assessment regarding various performance criteria including energy consumption and costs. During the design process, the involved experts from different disciplines frequently exchange building information to develop a design that satisfies the project’s requirements and objectives. In the course of this iterative process, the building design evolves throughout multiple refinement stages. At the same time, different variants are developed. In BIM-based projects, the maturity of the design information provided by the model is expressed by the notion of Level of development (LOD). So far, however, there is no method to formally define the information requirements of a LOD. In particular, there are no means for expressing the uncertainty involved with the provided information. By contrast, despite the insufficient information available in early design stages, a BIM model appears precise and certain. This situation leads to false assumptions and model evaluations, for example, in the case of energy efficiency calculations or structural analysis. Hence, this paper presents an overview of a set of approaches that were developed to alleviate and preserve the consistency of the designed solutions. The approach includes the development of a multi-LOD meta-model, which allows one to explicitly describe the LOD requirements of each building component type incorporating the possible uncertainties, e.g. concerning the building dimensions. On the basis of this multi-LOD model, methods for evaluating a building design’s performance regarding the building’s structure and life cycle energy performance are proposed that take the defined uncertainties into account. To support the management of design variants in one consistent model, a graph-based approach is introduced. Finally, a minimized communication protocol is described to facilitate the workflow and communicate the evaluation results for supporting the decision-making process.

The process of designing a building involves producing design concepts while fulfilling various requirements and regulations. Furthermore, during the project's life-cycle, multiple experts from multiple domains collaborate in developing the different partial models, including architectural, structural, and HVAC among others. Accordingly, clearly communicating the rationale behind design decisions is crucial for developing regulatory compliant designs that also fit the owner’s needs. The developed designs are the main deliverables exchanged and handed over. However, these deliverables do not include any explanation of design intentions or documentation of design decisions. Communication among parties and reuse of knowledge are hindered by the absent explanation of existing design. To overcome this deficiency, this paper proposes a methodology for digitally documenting design decisions, incorporating their intention and rationale. Architectural concepts and evaluation criteria are represented in the form of explanation tags as well as spatial and semantic constraints, which are assigned to the individual model elements and properties. Additionally, to document how design decisions fulfill owner requirements and regulatory documents, natural language processing (NLP) is employed to facilitate querying those documents and then the individual requirements are linked to specific elements, properties, and constraints. To evaluate the proposed methodology, a prototype was implemented as a plugin inside a BIM- Authoring tool and multiple real-world use cases are discussed.

Information models from the domains Building Information Modeling (BIM) and Urban Information Modeling (UIM) are generally considered as information silos due to their heterogeneous character. These information silos can be bridged through linking where corresponding objects are identified and linked subsequently. However, whether two objects are considered as corresponding might depend on the scenario for which the links are created. The dependency of the link creation and the scenario refers to the term contextual linking and is analyzed in this paper with respect to building and city models. Therefore, different situational aspects influencing the link creation are discussed. Afterwards, the issue of contextual linking is demonstrated based on three different integration scenarios. In summary, this paper has three major outcomes: First, this paper introduces an application-oriented perspective on information integration and emphasize the role of the application when linking heterogeneous information models. Second, this paper shows that linking heterogeneous information models from the domains BIM and UIM at instance level depends on the scenario. Third, the results of the discourse about contextual linking serve as a framework supporting the design and development of artifacts for linking heterogeneous information models from the domains BIM and UIM.