[SOLVED] Which IFC XSD should FreeCAD support?

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Moult
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[SOLVED] Which IFC XSD should FreeCAD support?

Postby Moult » Wed Jun 12, 2019 2:09 pm

I recently rebuilt the utility to extract a JSON data structure from IFC XSDs as shown here:

https://github.com/yorikvanhavre/BIM_Workbench/pull/26

It's been a while since an extract was run, so I will run it again. But the question is, which version of the XSD should I run it against? (see: https://technical.buildingsmart.org/sta ... fications/)

Should it be the latest ISO publication? (i.e. 4.0.2.1 IFC4 ADD2 TC1 ISO 16739-1:2018)

Or should it be the latest "official" release? (i.e. 4.1.0.0 IFC4.1 - 2018-06)
Last edited by Moult on Sun Jul 07, 2019 2:44 am, edited 1 time in total.
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Re: Which IFC XSD should FreeCAD support?

Postby yorik » Thu Jun 13, 2019 1:24 am

It's annoying... :D I would say let's go for the Add2, but before that, we should make sure IfcOpenShell supports it too maybe. I remember seeing talks about that but haven't looked more
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Re: Which IFC XSD should FreeCAD support?

Postby Moult » Thu Jun 13, 2019 12:54 pm

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Re: Which IFC XSD should FreeCAD support?

Postby ReD_CoDE » Fri Jun 14, 2019 3:01 am

For months you're looking for a thing that is through your eyes and you don't listen to me :lol: --> IFCDOCCCCCCCCCC

.ifcdoc is here:
IFC4 Addendum 2 Baseline (with MVD definitions of Reference View and Design Transfer View)
https://technical.buildingsmart.org/resources/ifcdoc/

This is why I say and you don't listen ;)
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Re: Which IFC XSD should FreeCAD support?

Postby Moult » Fri Jun 14, 2019 3:56 am

ReD_CoDE, there are a few issues with IfcDoc:

1. The baseline provided by IfcDoc is "IFC4_Add2_20160712" - in other words, the IFC doc file is 3 years old already. That version is not the latest "official" status version, and nor is it the latest ISO publication. That suggests that using the IFC doc file is not the correct approach.
2. IfcDoc is a Windows-only platform, so the only thing available to parse that is cross-platform is the STEP .ifcdoc file, of which there is only that version available. This is a bit limiting, compared to the full gamut of formats and versions available on the specs page. I will not be able to run the IfcDoc tool.
3. FreeCAD is tied to IfcOpenShell, so what we support has to be what IfcOpenShell also supports. This is unrelated to IfcDoc.

How does IfcDoc solve the problem? Perhaps I am misunderstanding something?
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Re: Which IFC XSD should FreeCAD support?

Postby ReD_CoDE » Fri Jun 14, 2019 4:04 am

I know, but you can extract "descriptions" you're looking for types or classed from it

For instance, when in the software there is "Address" you can include "the description provided inside the ifcdoc as guidance"

'IfcAddress','This abstract entity represents various kinds of postal and telecom addresses.....'
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Re: Which IFC XSD should FreeCAD support?

Postby Moult » Fri Jun 14, 2019 4:58 am

Ah yes, for descriptions the IfcDoc file helps, but only a bit - after all, if we want to support IFC4 ADD2 TC1, there is no IfcDoc for it. At this moment the only format that is available for all versions that we can programmatically scrape is the HTML format.
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Re: Which IFC XSD should FreeCAD support?

Postby ReD_CoDE » Fri Jun 14, 2019 9:00 am

Yes, then you have to convert HTML to XML or doc or any format you like
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Re: Which IFC XSD should FreeCAD support?

Postby Moult » Sun Jul 07, 2019 2:43 am

Marking this topic as closed.

We should match ifcopenshell's version, which is IFC4 ADD2 TC1.

Also, a closer look at IfcDoc reveals that it merely encapsulates the HTML of the web spec. Therefore parsing from the IfcDoc will require two levels of parsing, one for STEP, and another for the HTML DOM. This can be bypassed by simply downloading the HTML spec directly and parsing HTML immediately.
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