IFC 4.3.0.1 (IFC4X3) development

# 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

## 8.3.3.1.5 Formal representation

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