# 8.18.3.20 IfcTopologyRepresentation

## 8.18.3.20.1 Semantic definition

IfcTopologyRepresentation represents the concept of a particular topological representation of a product or a product component within a representation context. This representation context does not need to be (but may be) a geometric representation context. Several representation types for shape representation are included as predefined types:

The representation type is given as a string value at the inherited attribute 'RepresentationType'.

## 8.18.3.20.5 Formal representation

ENTITY IfcTopologyRepresentation
SUBTYPE OF (IfcShapeModel);
WHERE
WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items |
NOT('IFC4X3_DEV_d297a43.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
)) = 0

;
WR22 : EXISTS(SELF\IfcRepresentation.RepresentationType);
WR23 : IfcTopologyRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
END_ENTITY;