Problem

Certain property values can appear in multiple properties when exported to IFC.

Reason

This is because some of our IFC mapping statements use a 'first non-empty value of <list>' logic to ensure that the fields required for valid IFC and COBie output are populated. Architectural Spaces are the example where we are currently exporting OpenBuildings Designer properties as follows:

IFC Description  is     ArchSpace/@label
IFC LongName     is     first non-empty value of ("ArchSpace/@label2", "ArchSpace/@number", ArchSpace/@label)
IFC Name          is     first non-empty value of ("ArchSpace/@number", ArchSpace/@label)

if 'Label 2' and 'Space Number' properties are both empty the value of ABD's 'Label' property will be exported to all three IFC fields .

If 'Label 2' is empty the value of 'ArchSpace/@number' will appear twice.

Background

To ensure that the fields required for valid IFC and COBie generation always contain values we have applied the rules above rules to our IFC export to deal with situations where users have not entered data into all three properties:

• Label
• Label2
• Number

A value for the Label property is always provided by the delivered dataset content.

Label2 and Number values are site/project specific so are left empty for the entry of data as a project proceeds.

• Label - is intended to be the primary descriptive label for a space and is mapped to IFC Space Description.
• Label2 - is intended to contain additional descriptive labelling for the space. If a value is not entered for label2 it will use the value of Number, or if Number is empty it will use the value of Label.
• Number - is intended to contain the unique space number or identifying name, if a value is not entered it will use the value of Label.

Solution

The recommended solution is to enter values for both Label2 and Number properties either at placement or prior to IFC export using Dataset Explorer's "Edit in Excel" features. This will ensure the three properties contain appropriate values when exported.

An alternative solution is to edit the IFC mapping to set fixed mappings for 'Label 2' and 'Space Number', this can result in empty fields in the subsequent IFC export so is not recommended. 

This can be implemented by changing the appropriate values in the delivered dataset, e.g. in "C:\ProgramData\Bentley\AECOsimBuildingDesigner V8i Ss6\WorkSpace\BuildingDatasets\Dataset_SE\setting\IFC_PropertyMapping.set".

The delivered mappings in the Spatial Containment Types section are:

Space * * LongName * EVALUATE DG("ArchSpace/@label2", "ArchSpace/@number", "ArchSpace/@label")
Space * * Name * EVALUATE DG("ArchSpace/@number", "ArchSpace/@label")

Change these to

Space * * LongName * ArchSpace/@label2
Space * * Name * ArchSpace/@number

These values wil be read next time the IFC Export Wizard is started.