SummaryThe Xbim.Essentials library offers data extraction, data transformation and data validation functions for Building Information Models (BIM); its robust and optimised implementation allows efficient operations on gigabyte-range files for researchers and practitioners interested in the built environment.The library implements the complete object model of BuildingSMART's IFC schemas (2017) along with APIs for their management under the terms of the CDDL (Sun Microsystems 2005), which makes it also suitable for commercial research and development projects.Relevant fields of research span from social sciences to construction engineering and applied mathematics on account of the breadth of domains covered in the over 800 classes of the schema across building lifecycles.The project implements public APIs for:• Federating, merging and splitting models and entities within models (non-trivial because of cyclic and bi-directional relationships defined in the schemas).• Verification of data quality through EXPRESS WHERE clauses and metadata constraints.• programmatic management of IFC properties and relations through Schema Metadata.• Single point management of any IFC file, including XML, STEP21 and IFCZIP formats.Architectural features of the solution include:• Full access to the models through C# interfaces, allowing schema-agnostic data logic on any supported version.• Disk-based and in-memory options to suit diverse workflow infrastructures.• Log management for notification events where exceptions are not appropriate.Additionally, the Xbim.IO.TableStore namespace supports similar APIs, when conceptually suitable, on BuildingSMART's COBie object model (buildingSMART 2013), extending the domain of relevance to construction operations and facility management.Where appropriate, classes in the codebase are generated programmatically from the formal EXPRESS specification files (ISO 2013) ensuring full compliance with the standards. The library has been developed over many years and has supported several research projects such as iCAT
This research investigates the issues of authoring reusable BIM components that can be delivered across multiple platforms. A key constraint in the uptake of Building Information Modelling (BIM) technology is interoperability, the ability to accurately and automatically share and exchange data. This has been addressed by the creation of a system of standards; Industry Foundation Classes (Ifcs). Recognising the importance of Ifc standards, the promoters of many proprietary BIM software platforms generally claim that their products support them fully. This has been challenged, and the reported work has aimed to test these assertions. A simple test model was constructed to represent the various geometries that are encountered, which were then expressed in Ifc files. Fourteen commonly-used BIM software tools were subjected to tests in which the range of geometries within the test model was imported into each tool in Ifc format. A simple visual analysis of the outcomes showed a dramatic failure to process the geometries as they were intended. The results of the study indicate that the current commercial BIM authoring tools, whilst being technically capable of providing support for the required component geometric representations, are constrained from doing so by their conversion interfaces from Ifc geometries. The practical implications of this are considerable, and could result in the possibility of serious errors within designs for construction projects. This is particularly relevant in the case of the BIM library components that are currently being authored for importing into project design models. The test model has been circulated to experts in the area, and their observations, as well as results of any further tests will be made publicly available.
Ding and Kassem, Mohamad (2019) Geometric optimization of building information models in MEP projects: Algorithms and techniques for improving storage, transmission and display. Automation in Construction, 107. p. 102941.
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