Natural language names
Semantic definitions at the type
Type definition

A label is the term by which something may be referred to. It is a string which represents the human-interpretable name of something and shall have a natural-language meaning.

Type: STRING of up to 255 characters

NOTE  Type adapted from label defined in ISO 10303-41.
HISTORY  New type in IFC2x.
IFC4 CHANGE  Previously recommended size restriction of 255 characters is now mandatory.

Value restrictions

As a human-readable string for naming purposes, a label is usually human-specified and locale-dependent (in contrast to purely machine-readable identifiers, IfcIdentifier).

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.
Formal representations
XSD Specification
 <xs:simpleType name="IfcLabel">
  <xs:restriction base="xs:normalizedString">
   <xs:maxLength value="255"/>
 <xs:element name="IfcLabel-wrapper" nillable="true">
    <xs:extension base="ifc:IfcLabel">
     <xs:attributeGroup ref="ifc:instanceAttributes"/>
EXPRESS Specification
TYPE IfcLabel = STRING (255);

Link to EXPRESS-G diagram EXPRESS-G diagram

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