IfcBuildingElementPart represents major components as subordinate parts of a building element. Typical usage examples include precast concrete sandwich walls, where the layers may have different geometry representations. In this case the layered material representation does not sufficiently describe the element. Each layer is represented by an own instance of the IfcBuildingElementPart with its own geometry description.
Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object,
Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.
Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.
References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical structures only).
References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).
References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.
References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definition can be aggregated by several other objects (occurrences or parts).
References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definition can only be part of a single decomposition (to allow hierarchical structures only).
Reference to the relationship objects, that associates external references or other resource definitions to the object. Examples are the association to library, documentation or classification.
The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED or when the concrete entity instantiated does not have a PredefinedType attribute. The latter is the case in some exceptional leaf classes and when instantiating IfcBuiltElement directly.
Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.
Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.
Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type.
Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object.
This establishes the object coordinate system and placement of the product in space. The placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constrained (e.g. relative to grid axes, or to a linear positioning element). The type of placement is determined by the various subtypes of IfcObjectPlacement. An object placement must be provided if a representation is present.
Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case of a shape representation (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement.
Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.
Reference to the objectified relationship IfcRelReferencedInSpatialStructure may be used to relate a product to one or more spatial structure elements in addition to the one in which it is primarily contained.
The tag (or label) identifier at the particular instance of a product, e.g. the serial number, or the position number. It is the identifier at the occurrence level.
Reference to the interference relationship to indicate the element that is interfered. The relationship, if provided, indicates that this element has an interference with one or many other elements.
Reference to the interference relationship to indicate the element that interferes. The relationship, if provided, indicates that this element has an interference with one or many other elements.
Reference to the IfcRelVoidsElement relationship that creates an opening in an element. An element can incorporate zero-to-many openings. For each opening, that voids the element, a new relationship IfcRelVoidsElement is generated.
Reference to the connection relationship with realizing element. The relationship, if provided, assigns this element as the realizing element to the connection, which provides the physical manifestation of the connection relationship.
Containment relationship to the spatial structure element, to which the element is primarily associated. This containment relationship has to be hierarchical, i.e. an element may only be assigned directly to zero or one spatial structure.
Reference to IfcCovering by virtue of the objectified relationship IfcRelCoversBldgElements. It defines the concept of an element having coverings associated.
Reference to the IfcRelAdheresToElement relationship that adheres a IfcSurfaceFeature to an element. An element can incorporate zero-to-many surface features in one relationship.
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Either the PredefinedType attribute is unset (e.g. because an IfcBuildingElementPartType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.
Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject.
This concept can be applied to the following resources:
An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as IfcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.
Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case that the same property (within the same property set) is defined both in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.
The body or solid model geometric representation of an IfcProduct is typically defined using a Tessellation or Brep. Subtypes may provide recommendations on other representation types that may be used. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:
The geometric representation of any IfcProduct is provided by the IfcProductDefinitionShape allowing multiple geometric representations. It uses the Product Placement concept utilizing IfcLocalPlacement to establish an object coordinate system, in which all geometric representations are founded.
An IfcElement (so far no further constraints are defined at the level of its subtypes or by view definitions) may be represented as a single or multiple boundary representation models, which include advanced surfaces, usually referred to as NURBS surfaces. The 'AdvancedBrep' representation allows for the representation of complex free-form element shape.
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple Boundary Representation models (which are restricted to be faceted Brep's with or without voids). The Brep representation allows for the representation of complex element shape.
Figure 6.3.3.1.A — Building element body boundary representation
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a CSG primitive or CSG tree. The CSG representation allows for the representation of complex element shape.
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple surface models, based on either shell or face based surface models. It may also include tessellated models.
Figure 6.3.3.1.B — Element surface model representation
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a mixed representation, including surface and solid models.
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple tessellated surface models, in particular triangulated surface models.
The 'CoG', Center of Gravity, shape representation is used as a means to verify the correct import by comparing the CoG of the imported geometry with the explicitly provided CoG created during export.
Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented using the 'MappedRepresentation'. This shall be supported as it allows for reusing the geometry definition of a type at all occurrences of the same type. The results are more compact data sets.
The same constraints, as given for 'SurfaceOrSolidModel', 'SurfaceModel', 'Tessellation', 'Brep', and 'AdvancedBrep' geometric representation, shall apply to the IfcRepresentationMap.
Product placement with a Product Linear Placement template. It defines the local coordinate system based on the curve which is referenced by IfcLinearPlacement.RelativePlacement which is an IfcAxis2PlacementLinear.Location using an IfcPointByDistanceExpression.BasisCurve. The local coordinate system is based on the tangent of the curve at Location, its normal in the global Z plane and the cross product of the aforementioned vectors.
The mapped item, IfcMappedItem, should be used if appropriate as it allows for reusing the geometry definition of a type at all occurrences of the same type.
A single instance of a subtype of IfcElementComponent can stand for several
actual element components at once. In this case, the IfcShapeRepresentation
contains as many mapped items as there are element components combined within this
occurrence object.
Figure 6.3.3.1.D — Element component mapped representation
Representation identifier and type are the same as in single mapped representation.
The number of mapped items in the representation corresponds with the count of
element components in the IfcElementQuantity.
