## 8.8 IfcMaterialResource

### 8.8.1 Schema Definition

The schema IfcMaterialResource contains the types and entities that are used to define materials (substances, of which products are made of). Materials are defined generically.

> NOTE The references to the usage of materials is made from the relevant elements through the objectified relationship IfcRelAssociatesMaterial.

Material definitions are distinguished by how they apply to elements or element types and by their components (layers, profiles, parts).

Material designation can be made for standard element occurrences to support a limited range of their parametric representation using

1. a structured set of material layers IfcMaterialLayerSetUsage and how the layers relate to the reference axis or plane,
2. a structured set of material profiles IfcMaterialProfileSetUsage and how the profiles relate to the reference axis.

> NOTE Often specific subtypes of building elements are used to have such parametric representations associated, they use the common suffix 'StandardCase', for example IfcWallStandardCase, or IfcBeamStandardCase.

Material designation can be made for element occurrences or element types without applying a parametric meaning using

1. a set of material layers (with a specified configuration by sequence and thickness of material layers) IfcMaterialLayerSet, or
2. a set of material profiles (with a specified configuration by positioning and outline profile of material profiles) IfcMaterialProfileSet, or
3. a set of materials (without a specified configuration or structure) IfcMaterialConstituentSet, or
4. as fallback by a single material IfcMaterial (including composite materials),

These options are exposed for association with IfcElement or IfcElementType and their subtypes through a select type IfcMaterialSelect. The association is realized by the objectified relationship IfcRelAssociatesMaterial, accessible by the inverse relationship AssociatedTo. Some associations to specific material entities may be restricted as not being appropriate within the specialized element or element type definitions.

The following material properties and information sets can be assigned to an IfcMaterialDefinition, or only to a single IfcMaterial.

- Material properties;
- Material classification and material library reference;
- Material presentation in shape models (e.g. by color, hatching, rendering);
- Relation to the ingredients of a material composite.

> HISTORY New schema in IFC1.0

> IFC4 CHANGE Definition of material properties and their assignment to IfcMaterial or other appropriate options in IfcMaterialSelect is now fully captured by IfcExtendedMaterialProperties using the general IfcProperty approach. Specific predefined subtypes of IfcMaterialProperties are no longer available.

> DEPRECATION Material designation by using IfcMaterialList is deprecated and should not be used. The classification of materials should not be done using IfcMaterialClassificationRelationship anymore (entity type deprecated); the IfcExternalReferenceRelationship in IfcExternalReferenceResource schema should be used instead.

EXPRESS-G diagram