The main purposes of the IFC4 Addendum 2 are the improvement of the IFC4 Add 1specification documentation and the necessary enhancements of the schema and property sets that resulted from the ongoing pilot implementations of the first two Model View Definitions, the Reference View and the Design Transfer View. The main change related to improvements to the tessellated geometry for the Reference View, and the advanced boundary representation geometry for the Design Transfer View. All changes made are downward compatible.
Two additional schema enhancements have been added after intensive discussions and considerations:
new subtype of tessellated geometry enabling planar and polygonal boundaries with inner loops
new elementary surfaces and intersection curves for more stable definitions of advanced b-rep's (NURBS)
The documentation format has been further improved for readability. More interlinked definitions, now including property and quantity sets, ifcXML files for all examples, in addition to IFC files, etc.;
The use of concept templates (chapter 4) improved, updated to Version 1.1 of the mvdXML specification and including the snippet of the mvdXML for each template;
The use of concepts at relevant IFC Entities, including the snippets of the mvdXML specification for each concept root, optimized for documentation of the requested functionalities;
NOTE This part is currently still experimental and focuses on documentation of concepts, it requires further improvements before being used for automatic IFC file validation purposes;