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The essential requirement of a BIM project is the successful exchange of intelligent information between various software applications (and operating systems) through all stages of the construction process.
The concept of OpenBIM is based on the standardised format of IFC (Industry Foundation Classes) files for exchanging one or more BIM models between project participants.
Objectif BIM has an interesting article that will give you an initial view of IFC.
The challenge is to communicate the properties of the objects at the right time in relation to what stage the project is at.



What is IFC?

To facilitate the development of a non-proprietary standard, IFC was created by an industrial consortium formed by Autodesk in 1994 and known under the name of the IAI (Industry Alliance for Interoperability). It allows construction industry objects to be organised in digital model software. It’s derived from the STEP file, which makes it possible to describe the information of a product for every stage in its lifecycle. Described in the EXPRESS computer language, IFC has developed thirteen versions, including six major ones since 1997, which have continually improved the specification of data. The Model View Definition (MVD), for example, defines an additional branch in the IFC tree structure for specific uses.



IFC export

The export setting for the particular software is critical, as there are different workflows that meet certain design brief specifications depending on the requirements of the construction project management.
OpenBIM offers a production flow and a list of compatible IFC software applications according to workflow needs.

To enable correct exchange of models in IFC, the IFC exports can vary according to the software used. Depending on the type of actors or batches/professions with whom the exchanges take place, the requirements are not the same. For example, the export of a model to a design and construction department will not be the same as the one for the HVAC design department. The model must be prepared.



Example: Revit Export

Depending on the type of workflow, it is important to know in advance what information is to be included in the IFC export. This is part of the role of the BIM manager.
To allow automation of the export methodology, there is the option of saving the user’s property sets defined by a correlation table between the name of the exported property and the one in Revit. This generates a file of line of code which can be read like a text file.
In this way each actor can work with his property names and save his export presets for each type of exchange.



Exchanges in IFC can be complicated

The files are larger than the native format, you lose the documentation of details in 2D, and most significantly, 20% of the data is assigned randomly.



BIM objects and IFC

IFC is a format project that allows the data inside the building to be treated on a hierarchical basis. For example, a zone contains several buildings, which contain several levels, subdivided into several rooms. This tree structure incorporates inheritance of properties. IFC is not an object format, however. This means objects are static.



IFC and loss of data

The problem of loss of data is often related to the creation of objects and can degrade their intelligence.
For the IFC format, families of BIM objects are architectural containers. In fact, IFC uses 3D as a container to describe real building materials. They have rational parameters and each software application has various standard elements corresponding to the IFC containers.


In an ideal world, export should be easy. In reality, the rules suggested by ISO IFC have to be followed so that the objects are exported correctly. Certain families must be associated with IFC containers before export. A poor definition of the object in the model has direct consequences for the export of the content.



An online interoperability solution with the OpenBIM strategy

BIM&CO have developed a technology that enables the class of objects to be identified as well the data. This technology is built around the BIM&CO classification itself, mapped to the classifications most frequently used on the international market. BIM&CO separates the geometry from the data so that the objects can be prepared for IFC export. The BIM & CO property dictionary is connected to the IFC dictionary, which allows translation of the data into IFC when integrating BIM objects into the model. This improves IFC exchanges and exports. What’s more, the data can even be sent to commercial software applications such as FISA. These Software Partners thus benefit from the correctly defined properties for analysis of the models. At any point in your project, you can use the BIM&CO plug-ins to customise the properties throughout the lifecycle of the building.



Have you already encountered problems in IFC?

Share your experience in comments on this article.

face Raphaëlle Jerez-Grisel