An Approach for Data Extraction, Validation and Correction Using Geometrical Algorithms and Model View Definitions on Building Models

Abstract

The Industry Foundation Classes (IFC) cover a wide variety of subdomains in the construction industry. Model View Definitions (MVD) enable to specify a subset of the IFC schema to assess the content of a model for specific use cases and information exchanges.However, IFC and MVD paradoxically complexify the workflow since it requires a deep understanding of the schema combined with construction knowledge to carry out simple use cases such as quantity checking or data export. This gap between domain specific queries and their expression in a computerreadable language weakens the opportunities provided to the building industry by Building Information Modeling.Our research consists in the implementation of MVDs in a high-level programming language to extract data from building models, an assessment of the extraction results and geometrical processing algorithms to correct the explicit quantities and properties that are supplied as metadata alongside the elements in IFC building models.Geometrical processing can be used to reduce and eventually correct errors on property values. We use a generic geometrical representation of IFC entity instances and apply geometrical transformations on those to obtain geometrical shapes. Boolean operations are used to identify relationships between elements. Eventually, incorrect data values are corrected directly in the IFC models accordingly to the IFC schema.For instance, we authored an MVD to extract data pertaining to external walls from different IFC models and corrected the value of the IsExternal property of the models' IfcWall entities. This use case is of great importance for the cost estimation of a thermal renovation on a building as it gives a good estimate of the outer surface area of the building envelope.

Multi-disciplinary Use of Three-Dimensional Geospatial Information

“…In particular, research like [26] shows the state of the validity of geometric relationships such as space boundaries, wall connectivity and spatial containment and shows how problematic they are. Luttun and Krijnen [27] show the same for the IsExternal property metadata that signifies on a per-element basis whether an element is part of the external facade of the building. More fundamentally though, space boundary geometries depend on a complete building model being Fig.…”

An Inspection of IFC Models from Practice

“…Krijnen et al [34] shows that many of the assessed models did have errors in their definitions of space boundaries. Luttun and Krijnen [41] shows that many of the assessed models did have errors in their labelling of external elements (the 'IsExternal' property). In addition, the correct identification of building units and their function are important, as well as the modelling of spaces and thermal zoning in particular (possibly as IfcZones in version 4 of IFC).…”