# IFC4 **URL:** https://forums.buildingsmart.org/c/developers/schema-ifc4/81.md [Latest](https://forums.buildingsmart.org/latest.md) · [Categories](https://forums.buildingsmart.org/categories.md) · [Tags](https://forums.buildingsmart.org/tags.md) --- ## [About the IFC4 category](https://forums.buildingsmart.org/t/about-the-ifc4-category/3637)
**Author:** [@jwouellette](https://forums.buildingsmart.org/u/jwouellette)\ **Replies:** 0
This category is for the discussion of implementation of IFC4 in software. --- ## [IfcFaceBasedSurfaceModel documentation](https://forums.buildingsmart.org/t/ifcfacebasedsurfacemodel-documentation/6137)
**Author:** [@SJL](https://forums.buildingsmart.org/u/SJL)\ **Replies:** 1\ **Last updated:** [June 2, 2025, 7:11am UTC](https://forums.buildingsmart.org/t/ifcfacebasedsurfacemodel-documentation/6137 "2025-06-02T07:11:39Z")
In documentation it says “IFC4-CHANGE The entity has been deprecated and shall not be used. The entity IfcFacetedBrep shall be used instead.” However FacetedBrep is a solid model. IfcFaceBasedSurfaceModel is not (necess… --- ## [Using of Pset\_ElementSize](https://forums.buildingsmart.org/t/using-of-pset-elementsize/5369)
**Author:** [@vynoskov](https://forums.buildingsmart.org/u/vynoskov)\ **Replies:** 0\ **Last updated:** [May 13, 2024, 5:46am UTC](https://forums.buildingsmart.org/t/using-of-pset-elementsize/5369 "2024-05-13T05:46:00Z")
Hello everyone! I want to use in my model software standardized PropertySet Element Size (7.5.4.44 Pset\_ElementSize - IFC4.3.2.0 Documentation) for IfcController elements. But I found very amazing occasion. This Pset re… --- ## [Quenstion about IfcActor, IfcActorRole, IfcOrganziation](https://forums.buildingsmart.org/t/quenstion-about-ifcactor-ifcactorrole-ifcorganziation/5173)
**Author:** [@lukasadrian](https://forums.buildingsmart.org/u/lukasadrian)\ **Replies:** 8\ **Last updated:** [February 29, 2024, 4:36am UTC](https://forums.buildingsmart.org/t/quenstion-about-ifcactor-ifcactorrole-ifcorganziation/5173 "2024-02-29T04:36:27Z")
Hi, I just want to understand something about the IFC Entities. I created a simple IFC File with C# but no IFC-Viewer can’t show IfcActor, IfcActorRole or IfcOrganziation. With XBim Xplorer I can just see the Entities w… --- ## [Can the concept of Reference Geometry be applied to IfcVoidingFeature in the same way as IfcOpeningElement?](https://forums.buildingsmart.org/t/can-the-concept-of-reference-geometry-be-applied-to-ifcvoidingfeature-in-the-same-way-as-ifcopeningelement/5177)
**Author:** [@iwtk](https://forums.buildingsmart.org/u/iwtk)\ **Replies:** 1\ **Last updated:** [February 24, 2024, 8:11am UTC](https://forums.buildingsmart.org/t/can-the-concept-of-reference-geometry-be-applied-to-ifcvoidingfeature-in-the-same-way-as-ifcopeningelement/5177 "2024-02-24T08:11:57Z")
Hi! Can the concept of Reference Geometry be applied to IfcVoidingFeature in the same way as IfcOpeningElement? https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2\_TC1/HTML/link/ifcvoidingfeature.htm --- ## [IfcRelDefinesByObject - anyone using?](https://forums.buildingsmart.org/t/ifcreldefinesbyobject-anyone-using/4527)
**Author:** [@Theoryshaw](https://forums.buildingsmart.org/u/Theoryshaw)\ **Replies:** 3\ **Last updated:** [April 5, 2023, 12:13am UTC](https://forums.buildingsmart.org/t/ifcreldefinesbyobject-anyone-using/4527 "2023-04-05T00:13:49Z")
Does anyone know if there’s any applications, currently, that use IfcRelDefinesByObject? Here’s only one example, out in the wild, that includes it. --- ## [A number of interesting Revit IFC parsing errors.](https://forums.buildingsmart.org/t/a-number-of-interesting-revit-ifc-parsing-errors/4605)
**Author:** [@ian](https://forums.buildingsmart.org/u/ian)\ **Replies:** 12\ **Last updated:** [February 8, 2023, 9:03pm UTC](https://forums.buildingsmart.org/t/a-number-of-interesting-revit-ifc-parsing-errors/4605 "2023-02-08T21:03:20Z")
We have an IFC that is created by Revit. It is exhibiting some interesting parsing errors. It’s possible that our parser is being too strict, but this particular file also exhibits errors in ArchiCAD, but not in BlenderB… --- ## [List of changes between IFC versions?](https://forums.buildingsmart.org/t/list-of-changes-between-ifc-versions/4604)
**Author:** [@CarlosVasquez](https://forums.buildingsmart.org/u/CarlosVasquez)\ **Replies:** 3\ **Last updated:** [February 3, 2023, 7:31am UTC](https://forums.buildingsmart.org/t/list-of-changes-between-ifc-versions/4604 "2023-02-03T07:31:03Z")
Hello, Is there a list of all the changes that occurred between, for example, IFC2x3 and IFC4? Mostly interested in changes to entities/predefined types. For example, which entities have been renamed or deprecated, what… --- ## [How should I interpret this "deviating" pattern in the IFD4\_ADD2 spec ?](https://forums.buildingsmart.org/t/how-should-i-interpret-this-deviating-pattern-in-the-ifd4-add2-spec/4237)
**Author:** [@tomzeppenfeldt](https://forums.buildingsmart.org/u/tomzeppenfeldt)\ **Replies:** 4\ **Last updated:** [May 19, 2022, 7:52am UTC](https://forums.buildingsmart.org/t/how-should-i-interpret-this-deviating-pattern-in-the-ifd4-add2-spec/4237 "2022-05-19T07:52:23Z")
I am parsing the IFC4.exp to store the specification as a graph. All seems good, but I sometimes find “deviating” patterns. For instance in the EXPRESS definition of IfcElement ENTITY IfcElement ABSTRACT SUPERTYPE OF…