8.6.3.10 IfcLibraryReference

8.6.3.10.1 Semantic definition

An IfcLibraryReference is a reference into a library of information by Location (provided as a URI). It also provides an optional inherited Identification key to allow more specific references to library sections or tables. The inherited Name attribute allows for a human interpretable identification of the library item. Also, general information on the library from which the reference is taken, is given by the ReferencedLibrary relation which identifies the relevant occurrence of IfcLibraryInformation.

The IfcLibraryReference additionally provides the capability to handle multilingual library entries. The Language attribute then holds the language tag for the language used by the strings kept in the Name and the Description attribute.

Depending on the type of technology used by the library, different IfcLibraryReference.Identification identifiers will be appropriate:

Publisher	Technology	Identifier
ASHRAE	BACnet	32-bit decimal BACnetObjectIdentifier indicating type ID and instance ID (e.g.'12.15' for Digital Input #15).
Brick Development Team	Brick	Full URI with no abbreviation (e.g. 'http://example.org/digitaltwin#AHU01', not 'digitaltwin:AHU01')
IETF	IPv4	32-bit decimal address for an IPv4 network (e.g.'192.168.1.1').
IETF	IPv6	128-bit hexadecimal address for an IPv6 network.
IETF	MAC	48-bit hexadecimal form of MAC address.
ISOIEC	LonTalk	48-bit hexadecimal neuron ID.
OPCFoundation	OPC	Hierarchical ItemID in alphanumeric form (i.e. 'B204.Tank2.Temperature)
SmartLabs	Insteon	24-bit hexadecimal instance address.

Table 8.6.3.10.A

8.6.3.10.2 Entity inheritance

- IfcExternalReference

8.6.3.10.3 Attributes

#	Attribute	Type	Description
IfcExternalReference (4)
1	Location	OPTIONAL IfcURIReference	Location, where the external source (classification, document or library) can be accessed by electronic means. The electronic location is provided as an URI, and would normally be given as an URL location string. IFC4-CHANGE The data type has been changed from IfcLabel to IfcURIReference .
2	Identification	OPTIONAL IfcIdentifier	The Identification provides a unique identifier of the referenced item within the external source (classification, document or library). It may be provided as * a key, e.g. a classification notation, like NF2.3 * a handle * a uuid or guid It may be human readable (such as a key) or not (such as a handle or uuid) depending on the context of its usage (which has to be determined by local agreement). IFC4-CHANGE Attribute renamed from ItemReference for consistency.
3	Name	OPTIONAL IfcLabel	Optional name to further specify the reference. It can provide a human readable identifier (which does not necessarily need to have a counterpart in the internal structure of the document).
	ExternalReferenceForResources	SET [0:?] OF IfcExternalReferenceRelationship FOR RelatingReference	Reference to all associations between this external reference and objects within the IfcResourceObjectSelect that are tagged by the external reference. IFC4-CHANGE New inverse attribute added with upward compatibility.
Click to show 4 hidden inherited attributes
IfcLibraryReference (4)
4	Description	OPTIONAL IfcText	Additional description provided for the library reference. IFC4-CHANGE New attribute added at the end of the attribute list.
5	Language	OPTIONAL IfcLanguageId	The language in which a library reference is expressed. IFC4-CHANGE New attribute added at the end of the attribute list.
6	ReferencedLibrary	OPTIONAL IfcLibraryInformation	The library information that is being referenced.
	LibraryRefForObjects	SET [0:?] OF IfcRelAssociatesLibrary FOR RelatingLibrary	The library reference with which objects are associated. IFC4-CHANGE New inverse attribute.

Table 8.6.3.10.B

8.6.3.10.4 Formal representation

 ENTITY IfcLibraryReference
 SUBTYPE OF (IfcExternalReference);
	Description : OPTIONAL IfcText;
	Language : OPTIONAL IfcLanguageId;
	ReferencedLibrary : OPTIONAL IfcLibraryInformation;
 INVERSE
	LibraryRefForObjects : SET [0:?] OF IfcRelAssociatesLibrary FOR RelatingLibrary;
END_ENTITY;