IFC 4.3.x development

6.1.3.48 IfcStair

Change log

IFC4

additions where_rules CorrectPredefinedType
additions where_rules CorrectTypeAssigned
deletions where_rules WR1
modificationsattributes ShapeType is_optionalChanged from False to True
modificationsattributes ShapeType name Changed from ShapeType to PredefinedType

IFC4X1

modificationswhere_rules CorrectTypeAssigned definitionChanged from (sizeof(IsTypedBy) = 0) or ('ifc4.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType)) to (sizeof(IsTypedBy) = 0) or ('ifc4x1.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType))

IFC4X2

modificationswhere_rules CorrectTypeAssigned definitionChanged from (sizeof(IsTypedBy) = 0) or ('ifc4x1.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType)) to (sizeof(IsTypedBy) = 0) or ('ifc4x2.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType))

IFC4X3_RC3

modificationssupertype Changed from IfcBuildingElement to IfcBuiltElement
modificationswhere_rules CorrectTypeAssigned definitionChanged from (sizeof(IsTypedBy) = 0) or ('ifc4x2.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType)) to (sizeof(IsTypedBy) = 0) or ('ifc4x3_rc3.ifcstairtype' in typeof(self\IfcObject.IsTypedBy[1].RelatingType))

6.1.3.48.1 Semantic definitions at the entity

A stair is a vertical passageway allowing occupants to walk (step) from one floor level to another floor level at a different elevation. It may include a landing as an intermediate floor slab.

NOTE  Definition according to ISO 6707-1: Construction comprising a succession of horizontal stages (steps or landings) that make it possible to pass on foot to other levels.

The IfcStair shall either be represented:

  • as a stair assembly entity that aggregates all parts (stair flight, landing, etc. with own representations), or
  • as a single stair entity without decomposition including all representation directly at the stair entity.

NOTE  In case of an IfcStair being the aggregate of all parts of the stair the aggregation is handled by the IfcRelAggregates relationship, relating an IfcStair with the related IfcStairFlight and landings, IfcSlab with PredefinedType=LANDING. IfcRailing's belonging to the stair may also be included into the aggregation.

NOTE  Model View Definitions and implementer agreements may restrict the IfcStair being an assembly to not have an independent shape representation, but to always require that the decomposed parts have a shape representation. In this case, at least the 'Body' geometric representations shall not be provided directly at IfcStair if it is an assembly. The 'Body' geometric representation of the IfcStair is then the sum of the 'Body' shape representation of the parts within the decomposition structure.

HISTORY  New entity in IFC2.0.

IFC4 CHANGE Attribute ShapeType renamed to PredefinedType.

6.1.3.48.1 Attributes

# Attribute Type Description
IfcRoot
1 GlobalId IfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world.
2 OwnerHistory OPTIONAL IfcOwnerHistory 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,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
3 Name OPTIONAL IfcLabel 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.
4 Description OPTIONAL IfcText Optional description, provided for exchanging informative comments.
IfcObjectDefinition
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects 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.
Nests SET [0:1] OF IfcRelNests FOR RelatedObjects 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 strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
IsNestedBy SET [0:?] OF IfcRelNests FOR RelatingObject 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).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions 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.

> IFC4 CHANGE  The inverse attribute datatype has been added.
IsDecomposedBy SET [0:?] OF IfcRelAggregates FOR RelatingObject 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 definitions can be aggregated by several other objects (occurrences or parts).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
Decomposes SET [0:1] OF IfcRelAggregates FOR RelatedObjects 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 definitions can only be part of a single decomposition (to allow hierarchical strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects 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.
IfcObject
5 ObjectType OPTIONAL IfcLabel 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.
IsDeclaredBy SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects 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.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
Declares SET [0:?] OF IfcRelDefinesByObject FOR RelatingObject 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.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
IsTypedBy SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects 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.

> IFC4 CHANGE  New inverse relationship, the link to IfcRelDefinesByType had previously be included in the inverse relationship IfcRelDefines. Change made with upward compatibility for file based exchange.
IsDefinedBy SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects 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.

> IFC4 CHANGE  The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
IfcProduct
6 ObjectPlacement OPTIONAL IfcObjectPlacement 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 constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system.
7 Representation OPTIONAL IfcProductRepresentation Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (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.
ReferencedBy SET [0:?] OF IfcRelAssignsToProduct FOR RelatingProduct Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.
PositionedRelativeTo SET [0:?] OF IfcRelPositions FOR RelatedProducts
ReferencedInStructures SET [0:?] OF IfcRelReferencedInSpatialStructure FOR RelatedElements
IfcElement
8 Tag OPTIONAL IfcIdentifier 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.
FillsVoids SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement Reference to the IfcRelFillsElement Relationship that puts the element as a filling into the opening created within another element.
ConnectedTo SET [0:?] OF IfcRelConnectsElements FOR RelatingElement Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.
IsInterferedByElements SET [0:?] OF IfcRelInterferesElements FOR RelatedElement 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.

> NOTE  There is no indication of precedence between IsInterferedByElements and InterferesElements.

> IFC4 CHANGE New inverse relationship.
InterferesElements SET [0:?] OF IfcRelInterferesElements FOR RelatingElement 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.

> NOTE  There is no indication of precedence between IsInterferedByElements and InterferesElements.

> IFC4 CHANGE New inverse relationship.
HasProjections SET [0:?] OF IfcRelProjectsElement FOR RelatingElement Projection relationship that adds a feature (using a Boolean union) to the IfcBuildingElement.
HasOpenings SET [0:?] OF IfcRelVoidsElement FOR RelatingBuildingElement 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.
IsConnectionRealizationSET [0:?] OF IfcRelConnectsWithRealizingElements FOR RealizingElementsReference 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.
ProvidesBoundaries SET [0:?] OF IfcRelSpaceBoundary FOR RelatedBuildingElement Reference to space boundaries by virtue of the objectified relationship IfcRelSpaceBoundary. It defines the concept of an element bounding spaces.
ConnectedFrom SET [0:?] OF IfcRelConnectsElements FOR RelatedElement Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element.
ContainedInStructure SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements Containment relationship to the spatial structure element, to which the element is primarily associated. This containment relationship has to be hierachical, i.e. an element may only be assigned directly to zero or one spatial structure.
HasCoverings SET [0:?] OF IfcRelCoversBldgElements FOR RelatingBuildingElement Reference to IfcCovering by virtue of the objectified relationship IfcRelCoversBldgElement. It defines the concept of an element having coverings associated.
HasSurfaceFeatures SET [0:?] OF IfcRelAdheresToElement FOR RelatingElement Reference to the IfcRelAdheresToElement relationship that adheres a IfcSurfaceFeature to an element. An element can incorporate zero-to-many surface features in one relationship.
IfcBuiltElement
IfcStair
9 PredefinedType OPTIONAL IfcStairTypeEnum Predefined generic type for a stair that is specified in an enumeration. There may be a property set given specifically for the predefined types.

> NOTE  The PredefinedType shall only be used, if no IfcStairType is assigned, providing its own _IfcStairType.PredefinedType_.

> IFC4 CHANGE The attribute has been renamed from ShapeType and changed to be OPTIONAL with upward compatibility for file based exchange.

6.1.3.48.2 Entity inheritance

dot_inheritance IfcStair IfcStair IfcBuiltElement IfcBuiltElement IfcStair->IfcBuiltElement IfcBuiltElement_children 24 more... IfcBuiltElement_children->IfcBuiltElement IfcElement IfcElement IfcBuiltElement->IfcElement IfcElement_children 10 more... IfcElement_children->IfcElement IfcProduct IfcProduct IfcElement->IfcProduct IfcProduct_children 8 more... IfcProduct_children->IfcProduct IfcObject IfcObject IfcProduct->IfcObject IfcObject_children 5 more... IfcObject_children->IfcObject IfcObjectDefinition IfcObjectDefinition IfcObject->IfcObjectDefinition IfcContext IfcContext IfcContext->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

6.1.3.48.3 Definitions applying to General Usage

6.1.3.48.3.1 Axis 2D Geometry

The walking line is represented by a two-dimensional open curve as the axis. The curve is directed into the upward direction (direction has to be interpreted as specified at the subtypes of IfcCurve).

NOTE  The 'Axis' representation of IfcStair may be provided even if the IfcStair has components with own shape representations.

6.1.3.48.3.2 Body AdvancedBrep Geometry

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 refered to as NURBS surfaces. The 'AdvancedBrep' representation allows for the representation of complex free-form element shape.

NOTE  View definitions or implementer agreements may restrict or disallow the use of 'AdvancedBrep' geometry.

6.1.3.48.3.3 Body Brep Geometry

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.

 

Brep representation
EXAMPLE  As shown in Figure 150, the Brep representation is given by an IfcShapeRepresentation, which includes one or more items, all of type IfcFacetedBrep. In some cases it may be useful to also expose a simple representation as a bounding box representation of the same complex shape.

Figure 150 — Building element body boundary representation

 

6.1.3.48.3.4 Body CSG Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented a CSG primitive or CSG tree. The CSG representation allows for the representation of complex element shape.

NOTE  View definitions or implementer agreements may restrict or disallow the use of 'CSG' geometry.

6.1.3.48.3.5 Body SurfaceModel Geometry

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.

 

surface model
EXAMPLE  As shown in Figure 149, the surface model representation is given by an IfcShapeRepresentation, which includes a single item which is either an IfcShellBasedSurfaceModel, or an IfcFaceBasedSurfaceModel. In some cases it may also be useful to expose a simple representation as a bounding box representation of the same complex shape.

Figure 149 — Element surface model representation

 

6.1.3.48.3.6 Body SurfaceOrSolidModel Geometry

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.

6.1.3.48.3.7 Body SweptSolid Geometry

6.1.3.48.3.8 Body Tessellation Geometry

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.

6.1.3.48.3.9 Box Geometry

bounding box
EXAMPLE  Any IfcElement may be represented by a bounding box, which shows the maximum extend of the body within the object coordinate system established by the IfcObjectPlacement. As shown in Figure 148, the bounding box representation is given by an IfcShapeRepresentation that includes a single item, an IfcBoundingBox.

Figure 148 — Building element box representation

 

6.1.3.48.3.10 Classification Association

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.

6.1.3.48.3.11 CoG Geometry

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 explicily provided CoG created during export.

6.1.3.48.3.12 Element Decomposition

Geometric representation by aggregated elements

If the IfcStair has components (referenced by SELF\IfcObject.IsDecomposedBy) with own 'Body' representation, then no 'Body' representation shall defined for the IfcStair. The IfcStair shape is then represented by the geometric representation of its components. The components are accessed via SELF\IfcObject.IsDecomposedBy[1].RelatedObjects.

Figure 272 illustrates stair placement, where the IfcStair defines the local placement for all components and the common 'Axis' representation, and each component has its own 'Body' representation.

stair

Figure 272 — Stair placement

RelatedObjects
'IfcStairFlight'
'IfcSlab'
'IfcRailing'

6.1.3.48.3.13 Element Projecting

6.1.3.48.3.14 Element Voiding

6.1.3.48.3.15 FootPrint Geometry

Type Identifier
'GeometricCurveSet''FootPrint'
'Annotation2D' 'FootPrint'

6.1.3.48.3.16 Identity

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.

6.1.3.48.3.17 Mapped Geometry

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.

6.1.3.48.3.18 Material Solid

The material of the IfcStair is defined by the IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

Material information can also be given at the IfcStairType, defining the common attribute data for all occurrences of the same type. It is then accessible by the inverse IsDefinedBy relationship pointing to IfcStair.HasAssociations and via IfcRelAssociatesMaterial.RelatingMaterial to IfcMaterial. If both are given, then the material directly assigned to IfcStair overrides the material assigned to IfcStairType.

6.1.3.48.3.19 Object Predefined Type

6.1.3.48.3.20 Object Typing

RelatingType
'IfcStairType'

6.1.3.48.3.21 Object User Identity

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.

6.1.3.48.3.22 Placement

The following restriction may be imposed by view definitions or implementer agreements:

  • If the IfcStair establishes an aggregate, then all contained elements shall be placed relative to the IfcStair.ObjectPlacement.

6.1.3.48.3.23 Product Geometric Representation

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, within all geometric representations are founded.

NOTE  A detailed specification of how to apply the local placement and which shape representaions are applicable is provided at the level of subtypes of IfcProduct and is further determined by the model view definition and implementer agreements.

6.1.3.48.3.24 Product Local Placement

The object placement for any subtype of IfcElement is defined by the IfcObjectPlacement, either IfcLocalPlacement or IfcGridPlacement, which defines the local object coordinate system that is referenced by all geometric representations of that IfcElement.

HasPlacement
'IfcLocalPlacement'
'IfcLocalPlacement'

6.1.3.48.3.25 Product Placement

The Product Placement establishes the object coordinate system and is required, if a geometric shape representation is provided for this product.

6.1.3.48.3.26 Property Sets for Objects

PsetName
'Pset_StairCommon'
'Pset_ConcreteElementGeneral'
'Pset_PrecastConcreteElementFabrication'
'Pset_PrecastConcreteElementGeneral'
'Pset_EnvironmentalImpactIndicators'
'Pset_EnvironmentalImpactValues'
'Pset_Condition'
'Pset_ManufacturerOccurrence'
'Pset_ManufacturerTypeInformation'
'Pset_ServiceLife'
'Pset_Warranty'

6.1.3.48.3.27 Property Sets with Override

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.

6.1.3.48.3.28 Revision Control

Ownership, history, and merge state is captured using IfcOwnerHistory.

6.1.3.48.3.29 Spatial Containment

The IfcStair, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

  • the Spatial Containment (defined here), or
  • the Element Composition.
RelatingStructure
'IfcBuildingStorey'
'IfcBuilding'
'IfcSite'

6.1.3.48.4 Formal representations

ENTITY IfcStair
 SUBTYPE OF (IfcBuiltElement);
	PredefinedType : OPTIONAL IfcStairTypeEnum;
 WHERE
	CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR
 (PredefinedType <> IfcStairTypeEnum.USERDEFINED) OR
 ((PredefinedType = IfcStairTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
	CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR
  ('IFC4X3_DEV_a1492713.IFCSTAIRTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;