Brief documentation for the current UML encoding of IFC and issues

This is not a proposal but information and findings during the process of converting IFC and part of ifcDoc (Pset and Qset) to UML and use it in the IFC Rail and IFC Infra Extension projects.

[https://drive.google.com/file/d/1WbVf3cta4A5SiykBBEGJsDo4wIaMlzSM/view?usp=sharing](https://drive.google.com/file/d/1WbVf3cta4A5SiykBBEGJsDo4wIaMlzSM/view?usp=sharing)

Issues and remarks are highlighted. Some of the issues have already been discussed by people here.

Start by reviewing the linked Google Drive document and the issue's highlighted remarks. Compare the documented UML encoding of IFC and the referenced parts of ifcDoc, including Pset and Qset, in the context of the IFC Rail and IFC Infra Extension projects. Done should mean the current encoding and identified issues are documented, but the issue does not specify target files or an exact documentation format.

Written by the indexing model from the issue text.