After a couple of month I'd like to restart this former discussion about compatibility between "ABD objects" organized in family / part structure and Item Types as standard CONNECT Edition way how to attach custom data to elements.
The problem is that Item Types are ignored when objects are exported to IFC, regadless the object is generic MicroStation geometry, MicroStation geometry converted to ABD part or an object created by ABD tools. In GUI it looks like this:
... walls are correctly exported to IFC, but all Item Types (named Extra data in this case) are cut off and lost.
I agree with NigelPDavies (a quote from the original discussion):
Items are seemingly now the primary form of adding properties to MicroStation-speciifc applications and not being able to get that information over to a platform neutral ISO-standard file format (ie IFC) is becoming a crucial issue.
Often not everything is created in ABD, project participants can use MicroStation only to create specific parts of model, or the data can be shared from other solutions (e.g. Revit) using i-model. In such situation all EC data (Item Types) are lost, which is quite big problem. E.g. here in Czech Republic, based on government decisions from last year, all public building contract over some amount/size is required to be created in accordance to BIM from 2022. Because of this change with all building industry impact solution providers are closely cooperating with engineering and construction companies to be prepared (as far as I know Bentley has ignored it, I don't know about any such local Bentley activity).
When I talked with people from BIM SIG and BIM group, who try to be independent from one particular solution, they are quite pesimistic about using ABD to produce IFC and to use ItemTypes in any BIM worklow where IFC is a final format, because combination of products cannot ensure data will be maintained and not lost.
My questions are:
HI Jan, we asked internally about this. According to ABD product management we have no plans to integrate Items in export to IFC. The main reason given is that items are regarded as unstructured data. Now I'm not a Developer or a data system expert but I think I get the point. IFC is highly structured data construct that has relationships that establish a heirachy such as Site>building>floor>Space>Object roughly speaking. Any data that is exported to IFC needs to be able to record reproduce and map those relationships. Items allow people to create definitions on the fly but people might forget to create a field that implies a relationship to a floor or a building or a space which IFC needs.
I know that is far from a complete or accurate answer but in principle I thinks it explains our current position and why items might not work.
Bentley Systems, Manchester UK