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IFC Technology

HVAC model 3


IFC Standard

Industry Foundation Classes (IFC) are provided as EXPRESS and XSD definitions

Quick links for developers:

  • XSD

IFC Specification Technology

The IFC specification is written using the EXPRESS data definition language, defined as ISO10303-11 by the ISO TC184/SC4 committee. It is the same data definition language as used e.g. in STEP or CIS/2. It has the advantage of being compact and well suited to include data validation rules within the data specification. The IFC exchange file structure (the syntax of the IFC data file with suffix ".ifc") is the so called "STEP physical file" format, defined as ISO10303-21 by the same ISO TC184/SC4 committee. It is an ASCII file format used to exchange IFC between different applications.

In addition to the IFC-EXPRESS specification an ifcXML specification is published as well (since the IFC2x release). The ifcXML spec is provided as an XML schema 1.0, as defined by W3C. The ifcXML exchange file structure (the syntax of the IFC data file with suffix ".ifcXML") is the XML document structure. The XML schema is automatically created from the IFC-EXPRESS source using the "XML representation of EXPRESS schemas and data", defined as ISO10303-28 ed. 2. This ensures that both IFC-EXPRESS and ifcXML handle the same data consistently and that the *.ifc and *.ifcXML data files can be converted bi-directionally.