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by bernd on 11 Dec 2020, edited 16 Dec 2020
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I am not 100% sure, thus I made a post in buildingsmart forums, but noone answered. Does someone of you do know exactly what is allowed? https://forums.buildingsmart.org/t/what-character-are-allowed-for-a-ifcpropertysinglevalue-s-name/3186
cheers bernd
What is according ifc standard allowed to be used as key for a pset properties?
I found ...
https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcpropertyresource/lexical/ifcpropertysinglevalue.htm
according inheritance
https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcpropertyresource/lexical/ifcproperty.htm
the name is a IfcIdentifier
https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/schema/ifcmeasureresource/lexical/ifcidentifier.htm
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?
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by Moult on 12 Dec 2020
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+1 votes
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 https://en.wikipedia.org/wiki/ISO/IEC_8859-1 - 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.
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by bernd on 16 Dec 2020
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Thanks for giving your input on this. Cheers Bernd