IFC

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History and versions of IFC

History of IFC

The IFC initiative began in 1994, when Autodesk formed an industry consortium to advise the company on the development of a set of C++ classes that could support integrated application development. Twelve US companies joined the consortium. These companies included AT&T, HOK Architects, Honeywell, Carrier, Tishman and Butler Manufacturing. Initially named the Industry Alliance for Interoperability, the Alliance opened membership to all interested parties in September, 1995 and changed its name in 1997 to the International Alliance for Interoperability. The new Alliance was reconstituted as a non-profit industry-led organization, with the goal of publishing the Industry Foundation Classes (IFC) as a neutral AEC product model responding to the AEC building lifecycle. A further name change occurred in 2005, and the IFC specification is now developed and maintained by buildingSMART.

Versions of IFC

There were six principal releases of the IFC since the first version in 1996: IFC1.5.1, IFC2.0, IFC2x (the x is short for ‘extension’), IFC2x2 (so the second extension of IFC2), IFC2x3 (the third extension of IFC2) and IFC4 (formally known as IFC2x4) in 2013.

IFC 2×3

Version 2×3 of IFC was submitted to ISO and published in 2008 by ISO as ISO/PAS 16739:2005. PAS stands for “Publicly Available Standard;” in ISO, this term is used for “A normative document representing the consensus within a working group. … After six years, a PAS shall either be converted into an International Standard or be withdrawn.” In March 2013, Version 4 of IFC was approved as a full international standard (ISO 16739:2013).

IFC2x3 TC1

The IFC2x3 release and IFC2x3-TC1 update are equal in terms of the IFC exchange file and both are used for IFC2x3 implementation and certification.

The IFC2x3 technical corrigendum is to correct several known minor technical problems found since the release of the IFC2x3 specification and to improve the documentation generally.

A technical corrigendum typically is a collection of errata published separately from the specification to which they apply. Users are expected to insert the corrections by hand into their (printed) copy of the original specification. This process is basically infeasible with an electronic specification. The Model Support Group has chosen to release the corrected specification in its entirety but call it a technical corrigendum since it is fundamentally a correction of the existing specification rather than an expansion of scope and functionality.

A specific technical change in the TC was the modification of the defined type IfcCompoundPlaneAngleMeasure to allow optionally for the expression of angles to a fraction of a second. This change affected the specification (and existing software implementations) minimally but was an important first step in bringing the IFC and geospatial information specifications into alignment. This change allowed an IFC-specified building model to be referenced to a set of geospatial coordinates with the precision necessary for geospatial work.

Today, IFC2x3TC1 is referred to as IFC2x3 and it is the advised IFC version to use. Almost all exchanges of IFC in current practice are in 2×3.

IFC4

IFC4 (formerly IFC2x4) has been released as the new IFC platform for the upcoming years in 2013. It incorporates several extensions of IFC in building, building service and structural areas, enhancements of geometry and other resource components, and numerous quality improvements, fully integrated simple ifcXML specification, and a new documentation format.

Since initial publication, IFC Version 4 has been revised through two addenda published by buildingSMART International in July 2015 and July 2016. According to the IFC4 Add2 Release page, a new edition of ISO 16739 and certification for IFC4 will be based on the Add2 release. Certification will use “model view definitions” specified as IFC4 Design Transfer View V1.1 and IFC4 Reference View V1.1.

  • IFC4 Add1 – the first addendum of IFC4 incorporating necessary improvements that had been identified during the pilot implementations and the development activities for the first Model View Definitions.
  • The IFC4 Add1 was released in July 2015 as buildingSMART Final Standard and is the baseline for Model Views “IFC4 Reference View V1.0” and “IFC4 Design Transfer View V1.0”

IFC4 Add2 – the second addendum of IFC4 incorporating necessary improvements that had been requested before starting the IFC4 certification process for the IFC4 Reference View and the IFC4 Design Transfer View, in particular for improved geometry definitions.

  • The final version IFC4 Add2 was released in July 2016 as buildingSMART Final Standard and is the baseline for Model Views “IFC Reference View V1.1” and “IFC4 Design Transfer View V1.1”
  • IFC4 is in principle the fourth extension of IFC version 2. Therefore IFC2x3 is a subset of IFC4. Basically, IFC4 is the same schema as IFC2x3, but with additional features. In practice this is more nuanced and there are exceptions.

IFC5

IFC5 is currently in early planning phase, it is expected to include full support for various infrastructure domains and more parametric capabilities.

The first active project under buildingSMART International to expand IFC definition for the infrastructure domain is the IFC Alignment Project.