The Building and Construction industry globally continues to struggle to find clarity around the usefulness and correct application of Level of Development (LOD).
LOD is a measure of confidence and reliability of information at the various stages. When initially introduced, LOD filled a void and allowed project teams and particularly those downstream to understand the content and reliability of the model data they could expect to receive. Since its acceptance as a standard of reliability and integration within Building Information Modeling (BIM) and 3D models, it has been largely exposed to broader interpretation in relation to its application and what it is expected to deliver.
The LOD Specification document, published by the BIM Forum, http://bimforum.org/lod/ which is derived from the AIA G202-2013 Building Information Modeling Protocol Form document, helps to clarify the LOD concepts by objects and their attributes. It has now been adopted by many as a default industry standard and used as a basis for contracts. This may be pushing the LOD Specification too far. The LOD Specification is designed as a reference guide to assist the industry to specify the reliability of the information at each stage of projects.
Misinterpretation of the role and use of LOD, perhaps masks the bigger issue associated with building model data exchanges. For example, models are often now ill-defined as LOD 200 or LOD 300 rather than containing objects of a particular LOD level. Industry needs to agree on how to exchange data effectively and consistently throughout the project phases on a discipline to discipline basis – both geometric and non-geometric.
Information Delivery Manuals and Data Exchanges
The building industry globally needs a robust and reliable means of exchanging digital information that is machine readable and easy to check and validate at each stage of development.
buildingSMART, formerly the International Alliance for Interoperability (IAI), has since 1994, aimed to improve engagement and knowledge sharing amongst members and to take the lead in defining user needs and determining open BIM solutions for all, through internationally recognised standards, tools and training.
buildingSMART developed Industry Foundation Classes (IFC) to enable project teams to share information across the variety of software applications used for design, construction, procurement and ongoing operation of a building. At present it is considered the standard in rich data exchange. buildingSMART certifies applications that comply with IFC which provides a platform of industry wide acceptance and use in relation to how data is entered, used and extracted within the model.
buildingSMART developed the ISO 29481-1:2010 “Building information modelling – Information delivery manual – Part 1: Methodology and format” standard to capture and specify processes and information flow during the lifecycle of a building. The standard provides a methodology for the accurate exchange of data between parties, known as the Information Delivery Manual (IDM). This process helps to create the technical specifications of the project known as the Model View Definition (MVD). The beauty of MVD is that it allows different consultants and contractors to easily access the information relevant to their part of the build.
The Future is Data Exchanges
buildingSMART has a working group developing IDMs: http://iug.buildingsmart.org/idms/roadmap.
This roadmap covers the full range of project phases and seeks to identify discipline to discipline exchanges. These data exchanges are then more fully defined in MVDs that detail the objects and their properties (or attributes) that should be present. By defining these requirements, it is then possible to automate the exchange and checking of the embodied data. This helps to build confidence and reliability.
Examples are found on the buildingSMART IFC Solutions Factory site: http://www.blis-project.org/IAI-MVD/ . These exchanges are also put in the context of ‘Process Maps’ that have ‘Exchange Requirements’.
This is the level of detail in defining building data exchanges on a discipline to discipline basis at different project phases that I think we need in the industry.
The Concept Design BIM 2010 MVD, developed by GSA and CSI from USA, Statsbygg from Norway, and Senate from Finland, is a good place to look for further development of data exchanges. It covers Spatial Program Validation, Circulation/Security Analysis, Energy Performance Analysis and Quantity Takeoff, which enable four types of analyses early in the process to optimise the design and helps to see the application of MVDs.
A more focused IDM is the Information Delivery Manual for Structural Steel by AISC and Georgia Tech. It addresses the exchanges required by the structural steel industry with Exchange Models created by the architect, structural engineer or steel detailing engineer. Table 3 shows exchanges by project stages and the people who will create or receive them. The final table shows the attribute detail expected. https://www.aisc.org/WorkArea/showcontent.aspx?id=35502
Where to from here?
The IDM Roadmap shows the work still yet to be done to define and refine the full range of exchanges for industry, and buildingSMART welcomes assistance to make this happen.
The need to better define, produce and deliver building and construction data is an urgent issue. LOD has helped to identify the issue but we need to structure data exchan bges more simply for people and more precisely for software.
Perhaps the IDM and MVD work can help here.