After the last blog post and video about exporting Revit phases to IFC , I had an interesting discussion on LinkedIn about the possibilities of using statuses and tasks in IFC.
I then exchanged ideas with Dion Moult, who has a lot of experience with IFC in practice as well as in development, and share a short summary here - the whole conversation is available in my current YouTube video and I can only recommend anyone interested to watch or listen to it in full!
Basics
The IFC schema describes standard properties that are assigned to corresponding property sets. These are the properties that are relevant for most projects from the buildingSMART perspective - but their number is still considerable. The properties that occur in almost all projects are grouped in the so-called Common PropertySets and are supported by all common (certified) software solutions.
Here is an older blog post on this topic: https: //bim-me-up.com/allgemeine-ifc-eigenschaftensatze-common-property-sets/
What is the status in IFC?
In the IFC schema, most components have the STATUS property in the Common PropertySet, which can assume some predefined values (Enumerated values):
At first glance, this does not look dissimilar to the Revit phases - however, there are a few important differences and limitations:
- Revit has phase filters that enable the mapping of several phases in a project and form the current element status to a specific phase - in IFC, on the other hand, the status applies globally to the entire project, so that no complex projects can be mapped in an IFC using the status.
- Not all elements have the STATUS property in the IFC schema - for example, this is missing for spaces (IfcSpace), which is a restriction in many cases and requires the use of separate properties.
- The common IFC viewers do not have any preset "phase filters" - these usually have to be configured manually, which requires the user to have the relevant knowledge. This is also the reason why Revit only exports one phase by default and also excludes canceled elements from the export.
- The creation of filters in IFC viewers is made even more difficult by the fact that they generally require the specification of PropertySet (i.e. the property group) and the property (the actual property) - as STATUS is part of the common property sets, this is called differently for each IFC class, e.g. Pset_WallCommon for walls, Pset_BeamCommon for beams, Pset_WindowCommon for windows, etc. .e.g. Pset_WallCommon for walls, Pset_BeamCommon for beams, Pset_WindowCommon for windows, etc.
This must be taken into account when creating the filter rules and not all IFC viewers support filter rules with wildcards (*Common).
What are tasks in IFC?
The IFC schema has another definition that enables the mapping of complex tasks: IfcTask. This definition can be used for construction scheduling of complex construction projects, but is more comparable to scheduling tools than to phase planning in Revit.
Important: IfcTask is not part of the Coordination / Reference View MVD, which is used by buildingSMART for the certification of BIM authoring software, so it is not exported when exporting Revit or related products, for example. Admittedly, however, it must also be said that construction scheduling is not typically carried out in the planning software or by the architect, but in special tools that are intended for this purpose.
Conclusion
Due to the increasing importance of data and data workflows in our industry, it is becoming increasingly clear that authoring tools such as Revit only represent a relatively small part of the overall project or building lifecycle and that the most seamless and reliable data transfer possible is becoming more and more important.
Today, an IFC is a data package that transfers data from A to B. In the future, we will have to enrich these data packages with various tools throughout the entire life cycle - but both the tools and the IFC standard will have to evolve. As Dion says very aptly at the end:
The real benefit of IFC is the standardization, the core, the foundation that you can rely on, that is ISO standardized, and yes - we've talked today about some seemingly fundamental flaws in ISO, such as rooms not having status, but over time those flaws will be addressed, and over time we'll just get better and better as an industry.
Dion Moult