8.3.3.1 IfcConstraint

ABSTRACT This definition may not be instantiated

8.3.3.1.1 Semantic definition

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

8.3.3.1.2 Entity inheritance

8.3.3.1.3 Attributes

#	Attribute	Type	Description
IfcConstraint (9)
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 RelatedResourceObjects	Reference to an external references, e.g. library, classification, or document information, that are associated to the constraint. IFC4-CHANGE New inverse attribute.
	PropertiesForConstraint	SET [0:?] OF IfcResourceConstraintRelationship FOR RelatingConstraint	Reference to the properties to which the constraint is applied.

Table 8.3.3.1.A

8.3.3.1.4 Formal propositions

Name	Description
WR11	The attribute UserDefinedGrade must be asserted when the value of the IfcConstraintGradeEnum is set to USERDEFINED.
`(ConstraintGrade <> IfcConstraintEnum.USERDEFINED) OR ((ConstraintGrade = IfcConstraintEnum.USERDEFINED) AND EXISTS(SELF\IfcConstraint.UserDefinedGrade))`

Table 8.3.3.1.B

8.3.3.1.5 Formal representation

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;