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What character are allowed for a IfcPropertySingleValue s name

What is according ifc standard allowed to be used as key for a pset properties?

I found …

according inheritance

the name is a IfcIdentifier

Which would mean a property key (Its name in IFC) could be any alphanumeric string up to 255 characters including spaces and special characters like German Umlaute ä ü ö Merely most utf-8 character can be used for the key.

Would some one confirm this?

How about practic work. Do you guys out there use special character and spaces in property keys?

cheers bernd

At least one of our customers wishes to use characters with accents (for their own property set with names for the properties in French).

IfcIdentifier is defined as follows:

NOTE  The set of characters that may appear in STRINGs exchanged in the exchange structure as defined in ISO 10303.21 is provided in ISO 10646. The encoding of characters in case of file-based exchange is defined in ISO 10303-21 and ISO 10303-28. Among else, these specifications define the encoding of 8-bit characters from ISO 8859-1...-16 and of 2-byte and 4-byte Unicode characters from ISO 10646.

NOTE  While IfcIdentifier is restricted to 255 characters, the size in exchange files after encoding may be considerably larger than 255 octets, depending on the particular encoding and on the contents of the identifier.

If I view - I can see that the characters “ä ü ö” are allowed.

Alphanumeric may be most strictly interpreted to mean [A-Za-z0-9]. This may conflict with the note and disallow the accented characters. It may also disallow underscores and spaces.

Clearly, more clarity is required.

This would be very important to know because both are widely used in property keys.

I had a similiar case with the characters in another forum. It was the case of the subscribt number that is used in ISO 13501-2 for FireProtection such as:


I saw that the IFC Structure is capable to handle such numbers. The problem sometimes appears at the BIM Tool, which is not capable to interpret these numbers correctly.