IFC 4.3.x development

8.3.3.1 IfcConstraint

Change log

IFC4

modificationsattributes CreationTime definitionChanged from IfcDateTimeSelect to IfcDateTime
modificationsinverses ClassifiedAs definition Changed from SET OF [0:?] IfcConstraintClassificationRelationship FOR ClassifiedConstraint to SET OF [0:?] IfcExternalReferenceRelationship FOR RelatedResourceObjects
modificationsinverses ClassifiedAs name Changed from ClassifiedAs to HasExternalReferences

8.3.3.1.1 Semantic definitions at the entity

An IfcConstraint is used to define a constraint or limiting value or boundary condition that may be applied to an object or to the value of a property.

Constraints may be subdivided into user-defined constraints and system-defined constraints. User-defined constraints are applied by a user and are restricted to high-level definitions such as object properties. System-defined constraints may apply to any object attribute, are typically defined by an application to enforce data validation or parametric behavior, and are intended to be enforced by applications but not to be directly editable by an end-user.

IfcConstraint may be associated with any subtype of IfcObjectDefinition or IfcPropertyDefinition through the IfcRelAssociatesConstraint relationship to indicate a system-defined constraint, or may be associated with IfcResourceObjectSelect (such as IfcPropertySingleValue) by IfcResourceConstraintRelationship to indicate a user-defined constraint.

A constraint must have a name applied through the IfcConstraint.Name attribute and optionally, a description through IfcConstraint.Description. The grade of the constraint (hard, soft, advisory) must be specified through IfcConstraint.ConstraintGrade or IfcConstraint.UserDefinedGrade whilst the source, creating actor and time at which the constraint is created may be optionally asserted through IfcConstraint.ConstraintSource, IfcConstraint.CreatingActor and IfcConstraint.CreationTime.

A constraint may also have additional external information (such as classification or document information) associated to it by IfcExternalReferenceRelationship, accessible through inverse attribute IfcConstraint.HasExternalReferences

HISTORY  New entity in IFC2.0

IFC4 CHANGE  CreationTime changed to IfcDateTime for ISO 8601 representation, HasExternalReferences new inverse attribute.

8.3.3.1.1 Attributes

# Attribute Type Description
IfcConstraint
1 Name IfcLabel A human-readable name to be used for the constraint.
2 Description OPTIONAL IfcText A human-readable description that may apply additional information about a constraint.
3 ConstraintGrade IfcConstraintEnum Enumeration that qualifies the type of constraint.
4 ConstraintSource OPTIONAL IfcLabel Any source material, such as a code or standard, from which the constraint originated.
5 CreatingActor OPTIONAL IfcActorSelect Person and/or organization that has created the constraint.
6 CreationTime OPTIONAL IfcDateTime Time when information specifying the constraint instance was created.
7 UserDefinedGrade OPTIONAL IfcLabel Allows for specification of user defined grade of the constraint beyond the enumeration values (hard, soft, advisory) provided by ConstraintGrade attribute of type IfcConstraintEnum.

When a value is provided for attribute UserDefinedGrade in parallel the attribute ConstraintGrade shall have enumeration value USERDEFINED.
HasExternalReferences SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjectsReference to an external references, e.g. library, classification, or document information, that are associated to the constraint.

> IFC4 CHANGE New inverse attribute.
PropertiesForConstraintSET [0:?] OF IfcResourceConstraintRelationship FOR RelatingConstraint Reference to the properties to which the constraint is applied.

8.3.3.1.2 Entity inheritance

dot_inheritance IfcMetric IfcMetric IfcConstraint IfcConstraint IfcMetric->IfcConstraint IfcObjective IfcObjective IfcObjective->IfcConstraint

8.3.3.1.3 Formal representations

ENTITY IfcConstraint
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcMetric
	,IfcObjective));
	Name : IfcLabel;
	Description : OPTIONAL IfcText;
	ConstraintGrade : IfcConstraintEnum;
	ConstraintSource : OPTIONAL IfcLabel;
	CreatingActor : OPTIONAL IfcActorSelect;
	CreationTime : OPTIONAL IfcDateTime;
	UserDefinedGrade : OPTIONAL IfcLabel;
 INVERSE
	HasExternalReferences : SET [0:?] OF IfcExternalReferenceRelationship FOR RelatedResourceObjects;
	PropertiesForConstraint : SET [0:?] OF IfcResourceConstraintRelationship FOR RelatingConstraint;
 WHERE
	WR11 : (ConstraintGrade <> IfcConstraintEnum.USERDEFINED) OR
((ConstraintGrade = IfcConstraintEnum.USERDEFINED) AND EXISTS(SELF\IfcConstraint.UserDefinedGrade));
END_ENTITY;