IFC 4.3.0.1 (IFC4X3) development

8.6.3.1 IfcClassification

8.6.3.1.1 Semantic definition

An IfcClassification is used for the arrangement of objects into a class or category according to a common purpose or their possession of common characteristics. A classification in the sense of IfcClassification is taxonomy, or taxonomic scheme, arranged in a hierarchical structure. A category of objects relates to other categories in a generalization-specialization relationship. Therefore the classification items in an classification are organized in a tree structure.

The IfcClassification identifies the classification system or source to which a classification reference refers to. Each classification reference may reference an instance of IfcClassification. A classification system declared may be either formally published, or it may be a locally defined method of classifiying information.

There are two methods to define and reference a classification system:

  1. Including the classification system structure within the dataset: Here a hierarchical tree of IfcClassificationReference's is included that defines the classification system including the relationship between the classification items. The ReferencedSource attribute of IfcClassificationReference links the classification item to the parent item, and the parent item finally to the IfcClassification.
  2. Referencing the classification system by a classification key or id: Here the IfcClassificationReference is used to assign a classification id or key as Identification attribute and it may link by ReferencedSource attribute directly to the IfcClassification.

8.6.3.1.2 Entity inheritance

8.6.3.1.3 Attributes

# Attribute Type Description
IfcClassification (9)
1 Source OPTIONAL IfcLabel

Source (or publisher) for this classification.

2 Edition OPTIONAL IfcLabel

The edition or version of the classification system from which the classification notation is derived.

3 EditionDate OPTIONAL IfcDate

The date on which the edition of the classification used became valid.

4 Name IfcLabel

The name or label by which the classification used is normally known.

5 Description OPTIONAL IfcText

Additional description provided for the classification.

6 Specification OPTIONAL IfcURIReference

Resource identifier or locator, provided as URI, URN or URL, of the classification.

7 ReferenceTokens OPTIONAL LIST [1:?] OF IfcIdentifier

The delimiter tokens that are used to mark the boundaries of individual facets (substrings) in a classification reference.

This typically applies then the IfcClassification is used in conjunction with IfcClassificationReference's. If only one ReferenceToken is provided, it applies to all boundaries of individual facets, if more than one ReferenceToken are provided, the first token applies to the first boundary, the second token to the second boundary, and the n^th^ token to the n^th^ and any additional boundary.

ClassificationForObjects SET [0:?] OF IfcRelAssociatesClassification FOR RelatingClassification

The classification with which objects are associated.

HasReferences SET [0:?] OF IfcClassificationReference FOR ReferencedSource

The classification references to which the classification applies. It can either be the final classification notation, or an intermediate classification item.

Table 8.6.3.1.A

8.6.3.1.4 Formal representation

ENTITY IfcClassification
 SUBTYPE OF (IfcExternalInformation);
	Source : OPTIONAL IfcLabel;
	Edition : OPTIONAL IfcLabel;
	EditionDate : OPTIONAL IfcDate;
	Name : IfcLabel;
	Description : OPTIONAL IfcText;
	Specification : OPTIONAL IfcURIReference;
	ReferenceTokens : OPTIONAL LIST [1:?] OF IfcIdentifier;
 INVERSE
	ClassificationForObjects : SET [0:?] OF IfcRelAssociatesClassification FOR RelatingClassification;
	HasReferences : SET [0:?] OF IfcClassificationReference FOR ReferencedSource;
END_ENTITY;

8.6.3.1.5 References

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8.6.3.1.6 Changelog

  • attribute, Description
  • attribute, Location
  • attribute, ReferenceTokens
  • inverse attribute, HasReferences
  • attribute Edition optional, Changed from "False" to "True"
  • attribute EditionDate type, Changed from "IfcCalendarDate" to "IfcDate"
  • attribute Source optional, Changed from "False" to "True"
  • inverse attribute Contains name, Changed from "Contains" to "ClassificationForObjects"
  • inverse attribute Contains type, Changed from "SET OF [0:?] IfcClassificationItem FOR ItemOf" to "SET OF [0:?] IfcRelAssociatesClassification FOR RelatingClassification"
  • attribute Location name, Changed from "Location" to "Specification"