Natural language names
Semantic definitions at the type
Type definition

An identifier is an alphanumeric string which allows an individual thing to be identified. It may not provide natural-language meaning.

Type: STRING of up to 255 characters

NOTE  Type adapted from identifier defined in ISO 10303-41.
HISTORY  New type in IFC2x.
IFC 2x4 CHANGE  Previously recommended size restriction of 255 characters is now mandatory.

Value restrictions

As a merely machine-readable string for identification purposes, an identifier is usually machine-generated and locale-independent (in contrast to human-readable labels, IfcLabel).

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
XML Specification
 <xs:simpleType name="IfcIdentifier">
  <xs:restriction base="xs:normalizedString">
   <xs:maxLength value="255"/>
EXPRESS Specification
TYPE IfcIdentifier = STRING (255);

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcControl IfcProcess IfcPropertySetTemplate IfcResource IfcTypeObject IfcTypeProcess IfcTypeResource IfcElement IfcRelInterferesElements IfcAsset IfcOrganization IfcPerson IfcApproval IfcReference IfcClassification IfcClassificationReference IfcDocumentInformation IfcExternalReference IfcSimpleValue IfcBlobTexture IfcSurfaceTexture IfcPresentationLayerAssignment IfcComplexProperty IfcExtendedProperties IfcProperty IfcCoordinateReferenceSystem IfcProjectedCRS IfcApplication IfcTableColumn

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