8.6.3.4 IfcDatasetReference

8.6.3.4.1 Semantic definition

An IfcDatasetReference is a reference to the location of a dataset. The reference is given by a system interpretable Location attribute (a URL string) where the document can be found, and an optional inherited internal reference Identification, which refers to a system interpretable position within the dataset. The optional inherited Name attribute is meant to have meaning for human readers. Optional dataset metadata can also be captured through reference to IfcDatasetInformation. Furthermore, the optional Filter attribute can be used to provide a text as e.g. SQL, XQuery etc to filter out data when only a subset is relevant for the dataset reference.

8.6.3.4.2 Entity inheritance

- IfcExternalReference

8.6.3.4.3 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 Click to hide 4 inherited attributes
IfcDatasetReference (4)
4	Description	OPTIONAL IfcText	Description of the dataset reference for informational purposes.
5	ReferencedDataset	OPTIONAL IfcDatasetInformation	Information about the referenced dataset.
6	Filter	OPTIONAL IfcText	An optional text as e.g. SQL, XQuery etc to filter out data when only a subset is relevant for the dataset reference.
	DatasetRefForObjects	SET [0:?] OF IfcRelAssociatesDataset FOR RelatingDataset	The dataset reference with which objects are associated.

Table A

8.6.3.4.4 Formal propositions

Name	Description
WR1	A name should only be given, if no dataset information (including the dataset name) is attached.
`EXISTS(Name) XOR EXISTS(ReferencedDataset)`

Table B

8.6.3.4.5 Formal representation

ENTITY IfcDatasetReference
SUBTYPE OF (IfcExternalReference);
Description : OPTIONAL IfcText;
ReferencedDataset : OPTIONAL IfcDatasetInformation;
Filter : OPTIONAL IfcText;
INVERSE
DatasetRefForObjects : SET [0:?] OF IfcRelAssociatesDataset FOR RelatingDataset;
WHERE
WR1 : EXISTS(Name) XOR EXISTS(ReferencedDataset);
END_ENTITY;