Index Page

  Specification for IfcProductExtension  

EXPRESS Definition

EXPRESS-G Diagram

IDL Definition

Schema Semantic Definition

Core extensions, as the name implies, provide extensions to concepts rooted in the kernel. Core extensions are therefore the first refinement layer for abstract kernel constructs. Each core extension is a specialization of classes defined in the Kernel.

The IfcProductExtension schema at the core extension layer defines basic object concepts, used within the AEC/FM industry, basically Elements, Spaces, and a structuring hierarchy, which consists of Site, Building, and Building Storey. It also handles basic element connectivity and space boundaries.

Type IfcBuildingTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcBuilding. In the current release no distinction is made between the various possible types of Building.

NOTE: This type is new in IFC Release 1.5

ISSUE: See Issue I-108 for changes made in IFC Release 1.5. Enumeration:

Building

Type IfcBuildingStoreyTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcBuildingStorey. In the current release no distinction is made between the various possible types of Building Storey.

NOTE: This type is new in IFC Release 1.5

ISSUE: See Issue I-112 for changes made in IFC Release 1.5. Enumeration:

BuildingStorey

Type IfcConnectionTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the different types of connection relationships between Elements according to their path definition.

NOTE: This type is new in IFC Release 1.5

ISSUE: See Issue 112 for changes made in IFC Release 1.5. Enumeration:

AtPath	Connection point is located at path of the element.
Start	Starting point of element's path is located at the Connection
AtEnd	End point of element's path is located at the Connection
NotKnown	The location of the connection point is not known.

Type IfcOpeningTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcOpeningElement.

NOTE: This type is identical with IFC Release 1.0 type IfcOpeningTypeEnum

Enumeration:

Opening
Passage
Recess
Chase

Type IfcSiteTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcSite. In the current release no distinction is made between the various possible types on a Building Site.

NOTE: This type is new in IFC Release 1.5.

Enumeration:

BuildingSite

Type IfcSpaceTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcSpace.

NOTE: This type is identical with IFC Release 1.0 type IfcSpaceTypeEnum.

Enumeration:

Occupied
Technical
Circulation

Type IfcSystemTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcSystem.

NOTE: This type is identical with IFC Release 1.0 type IfcSystemTypeEnum

ISSUE: See issue I-102 for changes made in IFC Release 1.5.1. Enumeration:

ElectricalSystem
HvacSystem
LightingSystem
PlumbingSystem
StructuralSystem

Type IfcZoneTypeEnum

EXPRESS Definition

Type Semantic Definition

Definition from IAI: This enumeration defines the available Generic Types for IfcZone.

NOTE: This type is identical with IFC Release 1.0 type IfcZoneTypeEnum.

Enumeration:

Thermal
Daylighting
Equipment

Class IfcBuilding

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Building represents a structure that provides shelter for its occupants or contents and stands in one place. The Building is also used to provide a basic structuring hierarchy for the components of a building construction project (together with Site, Storey, and Space).

Buildings can be grouped into a building complex by virtue of the general grouping mechanism (IfcRelGroups). The Building Complex is now handled by a direct instantiation of IfcGroup with the GroupPurpose attribute = 'BuildingComplex'.

Building Sections shall be handled by the IfcZone, which may be composed of all spaces that belong to the section. This is a restriction of IFC Release 1.5.

NOTE: This entity is identical with IFC Release 1.0 entity IfcBuilding.

ISSUE: See Issue I-108, I-122, I-116 for changes made in IFC Release 1.5.
See Issue GI-012 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	GenericType	Predefined generic types are specified in an enumeration. A Property Type Definition is available for each generic type.	IfcBuildingTypeEnum	Building	Building	Building
OPT	calcTotalHeight	Calculated Total (physical) Height of the Building. Exposed as an attribute by file-based exchange.	IfcLengthMeasure	0.0	see type	0.0
OPT	calcSiteCoverage	Calculated Coverage of the Building Site Area that is occupied by the Building (Footprint). Exposed as an attribute by file-based exchange.	IfcAreaMeasure	0.0	see type	0.0
OPT	calcTotalVolume	Calculated Total (Gross) Volume of all spaces enclosed by the Building. Exposed as an attribute by file-based exchange.	IfcVolumeMeasure	0.0	see type	0.0
INV	ServicedBySystems	Set of relationships to Systems, that provides a certain service to the Building. The relationship is handled by the objectified relationship IfcRelServicesBuildings	SET [0.?] OF IfcRelServicesBuildings	n/a	n/a	NIL

Formal Propositions:

WR41	There shall be exactly one instance of the IfcRelContains objectified relationship that defines a Project Container, i.e. referencing an IfcProject to contain this instance of IfcBuilding.
WR42	There shall be zero or one instance of the IfcRelContains objectified relationship that defines a Site Container, i.e. referencing an IfcSite to contain this instance of IfcBuilding.

Informal Propositions

IR1	Products being contained by IfcBuilding using the IfcRelContains objectified relationship shall be Building Storeys, Spaces or Elements.

Interface Definitions

• I_Building

Runtime Type Definitions

Geometry Use Definitions

Object Geometry in Context

The geometric representation of IfcBuilding is given by the IfcProductShape and IfcLocalPlacement, allowing multiple geometric representation. Included are:

Local Placement

The Reference Geometry for IfcBuilding is defined in its supertype IfcProduct. It is defined by the

• IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations. The PlacementRelTo relationship of IfcLocalPlacement shall point to the IfcSite, if the containing site is defined for this building and if relative placement is used for this Building.

Standard Geometric Representation

The standard geometric representation (if the building has an independent geometric representation) of IfcBuilding is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation. Since the building shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the Building is exposed independently from its constituting Elements.

Currently, the usage of attribute driven geometry for IfcBuilding is not supported.

Advanced Geometric Representation

The advanced geometric representation (if the building has an independent geometric representation) of IfcBuilding is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation.

Currently, the usage of attribute driven geometry for IfcBuilding is not supported.

Arbitrary Geometric Representation

The arbitrary geometric representation of IfcBuilding is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for arbitrary representation.

Currently, there is no difference in the usage of standard, advanced or arbitrary geometric representations for IfcBuilding.

Class IfcBuildingElement

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The Building Element comprises all elements that are primarily part of the construction of a building, i.e., its structural and space separating system. Examples of Building Elements are walls, beams, or doors, they are all physically existent and tangible things. They are separated from other elements, since they are dealt with in separate AEC processes.

The IfcBuildingElement has an optional relationship to the IfcMaterialSelect, the select of Material definition types, either IfcMaterialComposite or IfcMaterialLayerSet. Where the IfcMaterialComposite just defines a list of Material used within the IfcBuildingElement, the IfcMaterialLayerSet also comprises the layout of layers (ordering and thickness). The type driven property sets, referenced by the subtypes of IfcBuildingElement, can be used to identify, which component uses what material.

NOTE: Identically with IFC Release 1.0 entity IfcBuildingElement, but comprising now manufactured building elements as well.

ISSUE: See issues I-105, I-120, I-190 for changes made in IFC Release 1.5

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
OPT	HasMaterial	Reference to the Material Definition for that Building Element, can be either a single Material or a Material Layer Set	IfcMaterialSelect	n/a	n/a	NIL
INV	ProvidesBoundaries	Reference to Space Boundaries by virtue of the objectified relationship IfcRelSeparatesSpaces. It defines the concept of an Building Element bounding Spaces	SET [0:?] OF IfcRelSeparatesSpaces	n/a	n/a	NIL
INV	HasOpenings	Reference to the Voids Relationship that creates an opening in an element. An element can incorporate zero-to-many openings.	SET [0:?] OF IfcRelVoidsElement	n/a	n/a	NIL
INV	FillsVoids	Reference to the Fills Relationship that puts the Element into the Opening within another Element.	SET [0:?] OF IfcRelFillsElement	n/a	n/a	NIL

Interface Definitions

• I_BuildingElement

Runtime Type Definitions

This class is not typed -- there is no type definition.

Geometry Use Definitions

There are no instances of this abstract class. However, subtypes of this class do have geometry defined.

Class IfcBuildingStorey

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The Building Storey has an elevation and typically represents a (nearly) horizontal aggregation of spaces that are vertically bound. Building Sections shall be handled by the IfcZone, which may be composed of all spaces that belong to the section. This is a restriction of the IFC Release 1.5.

NOTE: This entity is identical with IFC Release 1.0 entity IfcBuildingStorey

ISSUE: See issues I-112, I-114, I-115, I-116, I-192 for changes made in IFC Release 1.5.
See Issue GI-012 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	GenericType	Predefined generic types are specified in an enumeration. A Property Type Definition is available for each generic type.	IfcBuildingStoreyTypeEnum	Building Storey	Building Storey	Building Storey
	Elevation	Elevation of the base of this storey, relative to the site datum elevation	IfcLengthMeasure	0.0	see type	0.0
OPT	calcTotalHeight	Calculated height of this storey, from the bottom surface of the floor, to the bottom surface of the floor or roof above. Will be exposed as an attribute by file-based exchange.	IfcLengthMeasure	0.0	see type	NIL
OPT	calcTotalArea	Calculated gross floor area for the floor plate of this storey (horizontal projections). Will be exposed as an attribute by file-based exchange.	IfcAreaMeasure	0.0	see type	NIL
OPT	calcTotalVolume	Calculated gross volume for this storey. Will be exposed as an attribute by file-based exchange.	IfcVolumeMeasure	0.0	see type	NIL

Formal Propositions:

WR41	There shall be exactly one instance of the IfcRelContains objectified relationship that defines a ProjectContainer, i.e. referencing an IfcProject to contain this instance of IfcBuildingStorey.
WR42	There shall be exactly one instance of the IfcRelContains objectified relationship that defines a BuildingContainer, i.e. referencing an IfcBuilding to contain this instance of IfcBuildingStorey.

Informal Propositions

IR1	Products being contained by IfcBuildingStorey using the IfcRelContains objectified relationship shall be either Spaces or Elements.

Interface Definitions

• I_BuildingStorey

Runtime Type Definitions

Geometry Use Definitions

Object Geometry in Context

The geometric representation of IfcBuildingStorey is given by the IfcProductShape and IfcLocalPlacement, allowing multiple geometric representation. Included are:

Local Placement

The Reference Geometry for IfcBuildingStorey is defined in its supertype IfcProduct. It is defined by the

• IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations. The PlacementRelTo relationship of IfcLocalPlacement shall point to the IfcBuilding, if the containing building is defined for this building storey and if relative placement is used for this building storey.

Standard Geometric Representation

The standard geometric representation (if the building storey has an independent geometric representation) of IfcBuildingStorey is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation. Since the building storey shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building storey is exposed independently from its constituting Elements.

Currently, the usage of attribute driven geometry for IfcBuildingStorey is not supported.

Advanced Geometric Representation

The advanced geometric representation (if the building storey has an independent geometric representation) of IfcBuildingStorey is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation.

Currently, the usage of attribute driven geometry for IfcBuildingStorey is not supported.

Arbitrary Geometric Representation

The arbitrary geometric representation of IfcBuildingStorey is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for arbitrary representation.

Currently, there is no difference in the usage of standard, advanced or arbitrary geometric representations for IfcBuildingStorey.

Class IfcConnectionGeometry

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The IfcConnectionGeometry is used to describe the geometrical and topological constraints that facilitate the physical connection of two objects. It is envisioned as a control that applies to the IfcRelConnectsElements relationship. In IFC Release 1.5x it is restricted to just geometrical constraints and to Point connection types only.

NOTE: New class in IFC Release 1.5.

ISSUE: See issue I-101, I-305 for changes made in IFC Release 1.5.

Attribute and Relationship Definitions

Inherited Classes

No attributes and no formal propositions are defined at this level.

Interface Definitions

• I_ConnectionGeometry

Runtime Type Definitions

This control is not typed -- there is no type definition, since type driven attributes are not foreseen for controls in IFC Release 1.5.

Geometry Use Definitions

This abstract control does not carry additional geometry - there is no geometry use definition.

Class IfcElement

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Generalization of all components that make up an AEC product. Those elements can be located logically by an element container in a structuring hierarchy (here: building), described by calculated quantities and assigned with one or many performed functions. The latter copes with multifunctional elements.

Elements are physically existent objects, although they might be void elements, such as holes. Elements either remain permanently in the AEC product, or only temporarily, as formwork does. Elements can be either assembled on site or pre-manufactured and built in on site. Examples of elements in a building construction context are walls, floors, windows and recesses.

An Element can also be defined as an Element Assembly that is a group of semantically and topologically related Elements that forms a higher level part of the AEC product. Examples for Element Assembly are complete Roof Structures, made by several Roof Areas, or a Stair, composed by Flights and Landings.

Elements that performs the same function may be grouped by an "Element Group By Function". It is realized by an instance of IfcGroup with the GroupPurpose = 'ElementGroupByFunction".

NOTE: This is an enhanced version of the union of three IFC Release 1.0 entities: IfcElement, IfcManufacturedElement, and IfcAssembledElement.

ISSUE: See issues I-103, I-104 for changes made in IFC Release 1.5.
See issues GI-012, I-102 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
INV	ConnectedTo	Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.	SET [0:?] OF IfcRelConnectsElements	n/a	n/a	NIL
INV	ConnectedFrom	Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element.	SET [0:?] OF IfcRelConnectsElements	n/a	n/a	NIL
INV	IsAssemblyThrough	Reference to the assemble relationship, that creates element assemblies. It defines via the RelatingObject side this Element as the assembly of other Elements.	SET [0:1] OF IfcRelAssemblesElements	n/a	n/a	NIL
INV	PartOfAssembly	Reference to the assemble relationship, that creates element assemblies.	SET [0:1] OF IfcRelAssemblesElements	n/a	n/a	NIL

Formal Propositions:

WR41

There shall be exactly one instance of the IfcRelContains objectified relationship that defines a ProjectContainer, i.e. referencing an IfcProject to contain this instance of IfcBuildingStorey.

WR42

The allowed subtypes of IfcProduct that can act as element containers are: IfcSpace, IfcSite, IfcBuilding, and IfcBuildingStorey. NOTE: This rule replaces the former SELECT type IfcElementContainer. There shall be only one instance of the IfcRelContains objectified relationship that contains (ContainedOrReferenced = TRUE) this instance of IfcElement. The relationship type shall therefore be SiteContainer, BuildingContainer, BuildingStoreyContainer, or SpaceContainer.

Interface Definitions

• I_Element

Runtime Type Definitions

This class is not typed -- there is no type definition.

Geometry Use Definitions

There are no instances of this abstract class. However, subtypes of this class do have geometry defined.

Class IfcLineConnectionGeometry

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The IfcLineConnectionGeometry is used to describe the geometrical constraints that facilitate the physical connection of two objects at a line (IfcPolyline). It is envisioned as a control that applies to the IfcRelConnectsElements relationship.

NOTE: This entity refers to the IFC Release 1.0 entity IfcEdgeConnector

ISSUE: New class in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	LineOnRelatingElement	Line at which connected objects are aligned at the Relating Element, given in the LCS of the Relating Element.	IfcPolyline	n/a	n/a	see type
OPT	LineOnRelatedElement	Line at which connected objects are aligned at the Related Element, given in the LCS of the Related Element. If the information is omitted, than the Origin of the Related Element is used.	IfcPolyline	n/a	n/a	NIL

Interface Definitions

• I_LineConnectionGeometry

Runtime Type Definitions

This control is not typed -- there is no type definition, since type driven attributes are not foreseen for controls in IFC Release 1.5.

Geometry Use Definitions

The Polyline defines the line segments, where the basic geometry items of the connected Element connects.

Class IfcOpeningElement

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Opening Element stands for opening, recess or chase, all reflecting voids. It represents a void within any element that has physical manifestation. Openings must be handled by all sectors and disciplines in AEC/FM industry, therefore the interoperability for Opening Elements is provided at this high level.

NOTE: This entity is identical with the IFC Release 1.0 entity IfcOpeningElement.

ISSUE: See Issue GI-012 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	GenericType	Predefined generic types are specified in an enumeration. A Property Type Definition is available for each generic type.	IfcOpeningTypeEnum	Opening	Chase	Opening
OPT	calcOpeningArea	Total Gross (physical) Area of the opening area (front view). Exposed as an attribute by file-based exchange, particularly for receiving applications with limited (or not existing) geometric capabilities.	IfcAreaMeasure	0.0	see type	NIL
INV	VoidsElements	Reference to the Voids Relationship that uses this Opening Element to create a void within an Element. The Opening Element can only be used to create a single void within a single Element.	SET [0:1] OF IfcRelVoidsElement	n/a	n/a	NIL
INV	HasFillings	Reference to the Filling Relationship that is used to assign Elements as Fillings for this Opening Element. The Opening Element can be filled with zero-to-many Elements.	SET [0:?] OF IfcRelFillsElement	n/a	n/a	NIL

Formal Propositions:

WR51	The Type Defined Property for Opening Elements shall have IfcOpeningElement as TypedClass attribute value.

Interface Definitions

• I_OpeningElement

Runtime Type Definitions

Geometry Use Definitions

Object Geometry in Context

The geometric representation of IfcOpeningElement is given by the IfcProductShape and IfcLocalPlacement allowing multiple geometric representations. Included are:

Local Placement

The Reference Geometry for IfcOpeningElement is defined in its supertype IfcProduct. It is defined by the

• IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

Standard Geometric Representation

The standard geometric representation of IfcOpeningElement is defined using the attribute driven geometry. The following constraints apply to the standard representation:

• Solid: IfcAttDrivenExtrudedSolid is required, referring to a single segment.
• Segment: IfcAttDrivenExtrudedSegment is required.
• Profile: IfcRectangleProfileDef shall be supported.
• Extrusion: The profile shall be extruded horizontally, e.g. for wall openings, or vertically e.g., for floor openings.

Example for standard geometric representation:

 

Extrusion  Extrusion path, for standard representation given by IfcAttDrivenExtrudedSolid referencing a single IfcAttDrivenExtrudedSegment  Default Type: IfcAttDrivenExtrudedSegment  IfcAttDrivenExtrudedSegment.Depth, Extrusion path defined by a positive length measure along the local z-axis Profile  Extrusion profile, for standard representation given by IfcAttDrivenExtrudedSegment referencing IfcAttDrivenProfileDef   Default Type: IfcRectangleProfileDef  YDim interpreted as Opening Height, XDim interpreted as Opening Width. Other Types: IfcArbitraryProfileDef  IfcBoundedCurve (closed and 2D) defining an arbitrary opening shape Extrusion Direction  The opening profile is extruded horizontally, i.e. in the direction of the thickness of the penetrated wall.  Placement  [Black arrows] The local placement of opening is placed relative to the co-ordinate system of the building element which is voided by the opening.  [Red arrows] The segment is placed relative to the local placement.  [Green arrows] The profile is placed relative to the XY plane of the placement co-ordinate system of the segment.

 

Advanced Geometric Representation

The advanced geometric representation of IfcOpeningElement is defined using the attribute driven geometry. The following constraints apply to the advanced representation:

• Solid: IfcAttDrivenExtrudedSolid is required, referring to a single or multiple segments.
• Segment: IfcAttDrivenExtrudedSegment is required.
• Profile: IfcRectangleProfileDef and IfcArbitraryProfileDef shall be supported.
• Extrusion: All extrusion directions shall be supported. This would provide support of openings in sloped building elements.

Example for advanced geometric representation:

 

Extrusion  Extrusion path, for standard representation given by IfcAttDrivenExtrudedSolid referencing multiple (here two) IfcAttDrivenExtrudedSegment. Hereby openings with shaped reveals are supported.  Default Type: Set of IfcAttDrivenExtrudedSegment  IfcAttDrivenExtrudedSegment[1..n].Depth, Extrusion paths defined by a positive length measure along the local z-axis. Profile  Extrusion profile, for standard representation given by each IfcAttDrivenExtrudedSegment referencing IfcAttDrivenProfileDef   Default Type: IfcRectangleProfileDef  YDim interpreted as Opening Height, XDim interpreted as Opening Width. Other Types: IfcArbitraryProfileDef  IfcBoundedCurve (closed and 2D) defining an arbitrary opening shape Extrusion Direction  The opening profile is extruded in the direction of the thickness of the penetrated sloped roof slab, i.e. an arbitrary extrusion direction.  Placement  [Black arrows] The local placement of opening is placed relative to the co-ordinate system of the building element which is voided by the opening.  [Red and brown arrows] The segments are placed relative to the local placement.  [Green and blue arrows] The profiles are placed relative to the XY planes of the placement co-ordinate systems of the segments.

Arbitrary Geometric Representation

The arbitrary geometric representation of IfcOpeningElement is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for arbitrary representation.

Class IfcPointConnectionGeometry

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The IfcPointConnectionGeometry is used to describe the geometrical constraints that facilitate the physical connection of two objects at a point (IfcCartesianPoint). It is envisioned as a control that applies to the IfcRelConnectsElements relationship.

NOTE: This entity refers to the IFC Release 1.0 entity IfcPointConnector

ISSUE: See issue I-101, I-305 for changes made in IFC Release 1.5.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	PointOnRelatingElement	Point at which connected objects are aligned at the Relating Element, given in the LCS of the Relating Element.	IfcCartesianPoint	n/a	n/a	see type
OPT	PointOnRelatedElement	Point at which connected objects are aligned at the Related Element, given in the LCS of the Related Element. If the information is omitted, than the Origin of the Related Element is used.	IfcCartesianPoint	n/a	n/a	NIL

Interface Definitions

• I_PointConnectionGeometry

Runtime Type Definitions

This control is not typed -- there is no type definition, since type driven attributes are not foreseen for controls in IFC Release 1.5.

Geometry Use Definitions

The Cartesian Point defines the point, where the basic geometry items of the connected Element connects.

Class IfcRelAssemblesElements

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified Relationship that assembles various Elements (or other Element Assemblies) into an Element Assembly. The Elements shall have a strong semantic and topological relationship and shall make up a new component within the AEC product.

NOTE: New entity in IFC Release 1.5

ISSUE: See issue I-106 for changes made in IFC Release 1.5.
See Issue GI-012 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingElement	Element that is defined as Assembly by virtue of this relationship.	IfcElement	n/a	n/a	NIL
	RelatedElements	Elements being part of the assembly.	LIST [1:?] OF IfcElement	n/a	n/a	NIL

Formal Propositions:

WR31	The instance to which the relation points shall not be contained in the List of RelatedObjects.

Informal Propositions:

IR1	The IfcRelAssemblesElements relationship shall be defined acyclic.

Interface Definitions

• I_RelAssemblesElements

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcRelAssemblesSpaces

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified Relationship that assembles various partial Spaces (or other Space Assemblies) into a Space Assembly. The Spaces shall have a strong semantic and topological relationship and shall make up a new Space with well defined boundaries. For non topological related Space groups use IfcZone.

NOTE: New entity in IFC Release 1.5

ISSUE: See issue I-106 for changes made in IFC Release 1.5.
See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingElement	Element that is defined as Assembly by virtue of this relationship.	IfcElement	n/a	n/a	see type
	RelatedElements	Elements being part of the assembly.	LIST [1:?] OF IfcElement	n/a	n/a	see type

Formal Propositions:

WR31	The instance to with the relation points shall not be contained in the List of RelatedObjects.

Informal Propositions:

IR1	The IfcRelAssemblesElements relationship shall be defined acyclic.

Interface Definitions

• I_RelAssemblesSpaces

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcRelConnectsElements

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Generalization of the connectivity between Elements. Based on this special type of 1 to 1 relationship, the concept of two elements being physically or logically connected is described independently from the connecting elements.

Currently (in IFC Release 1.5x) the connectivity is related to geometric entities on which the connection of the underlying basic geometry of the connecting elements occurs. This will be enhanced and/or replaced in later versions of the IFC model by a proper topological model. The geometrical constraints of the connection are provided by the optional relationship to the IfcConnectionGeometry control. If it is omitted then the connection is provided as a logical connection. Under this circumstance, the connection point, curve or surface has to be recalculated by the receiving application.

NOTE: This supertype is new in IFC Release 1.5

ISSUE: See issue I-189, I-304 for changes made in IFC Release 1.5.
See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
OPT	ConnectionGeometry	Relationship to the control class, that provides the geometrical constraints of the connection.	IfcConnectionGeometry	n/a	n/a	NIL
	RelatingElement	Reference to an Element that is connected by the objectified relationship.	IfcElement	n/a	n/a	see type
	RelatedElement	Reference to an Element that is connected by the objectified relationship.	IfcElement	n/a	n/a	see type

Interface Definitions

• I_RelConnectsElements

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

No geometric information about the connection is defined at the supertype.

Class IfcRelConnectsPathElements

EXPRESS Definition

Class Semantic Definition

Definition from IAI: The IfcRelConnectsPathElements provides the connectivity information between two Elements. The objectified relationship provides all additional information requirements to describe the connection between two path based elements that might have single or multiple layers of material.

NOTE: This supertype is new in IFC Release 1.5

ISSUE: See issue I-189, I-304 for changes made in IFC Release 1.5

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingPriorities	Priorities for connection, if given, it overwrites the default priorities at the IfcMaterialLayer class. It refers to the layers of the RelatingObject.	LIST [0:?] OF INTEGER	0	Relating Layer Count	0
	RelatedPriorities	Priorities for connection, if given, it overwrites the default priorities at the IfcMaterialLayer class. It refers to the layers of the RelatedObject	LIST [0:?] OF INTEGER	0	Related Layer Count	0
	RelatingConnectionType	Indication of the connection type in relation to the path of the RelatingObject.	IfcConnectionTypeEnum	AtPath	NotKnown	AtEnd
	RelatedConnectionType	Indication of the connection type in relation to the path of the RelatingObject.	IfcConnectionTypeEnum	AtPath	NotKnown	Start
DER	RelatingLayerCount	No of layers of the RelatingObject	INTEGER	1	see type	1
DER	RelatedLayerCount	No of layers of the RelatedObject	INTEGER	1	see type	1

Interface Definitions

• I_RelConnectsPathElements

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

No geometric information about the connection is defined at the supertype.

Class IfcRelFillsElement

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified relationship between an opening element and building elements that fill (or partially fill) the opening element.

NOTE: This entity is identical with IFC Release 1.0 entity IfcRelFills with the exception that it now references Element instead of Filling Element.

ISSUE: See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingOpeningElement	Opening Element being filled by virtue of this relationship	IfcOpeningElement	n/a	n/a	see type
	RelatedBuildingElement	Element that occupy fully or partially the associated opening	IfcBuildingElement	n/a	n/a	see type

Interface Definitions

• I_RelFillsElement

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcRelSeparatesSpaces

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified relationship that handles the Element to Space relationship by objectifying the relationship between an Element and a Space Boundary.

NOTE: This entity refers to IFC Release 1.0 entity IfcRelSpaceSeparation

ISSUE: See issue I-120 for changes made in IFC Release 1.5.
See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingBuildingElement	Reference to Building Element, that defines the Space Boundaries	IfcBuildingElement	n/a	n/a	NIL
	RelatedSpaceBoundaries	Reference to a set of Space Boundaries that are defined by the relating Element.	LIST [1:?] OF IfcSpaceBoundary	n/a	n/a	NIL

Interface Definitions

• I_RelSeparatesSpaces

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcRelServicesBuildings

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified Relationship that defines the relationship between a System and the Buildings it serves.

NOTE: This entity is identical with IFC Release 1.0 entity IfcRelServicesBuildings except that it now is subtyped from IfcRelationship.

ISSUE: See issues I-089, I-111 for changes made in IFC Release 1.5.
See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingSystem	System that services the Buildings.	IfcSystem	n/a	n/a	see type
	RelatedBuildings	Buildings that are serviced by the System	LIST [1:?] OF IfcBuilding	n/a	n/a	see type

Interface Definitions

• I_RelServicesBuildings

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcRelVoidsElement

EXPRESS Definition

Class Semantic Definition

Definition from IAI: Objectified Relationship between an building element and one opening element that creates a void in the element. This relationship implies a Boolean Operation of subtraction for the geometric bodies of Element and Opening Element.

NOTE: This entity is identical with IFC Release 1.0 entity IfcRelVoid, except that it now references Element instead of Building Element.

ISSUE: See Issue I-310 for changes made in IFC Release 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	RelatingBuildingElement	Element in which a void is created by associated Opening Elements	IfcBuildingElement	n/a	n/a	see type
	RelatedOpeningElement	Opening Elements which define voids in the associated Element	IfcOpeningElement	n/a	n/a	see type

Interface Definitions

• I_RelVoidsElement

Runtime Type Definitions

Objectified relationships are not typed -- there is no type definition, since type driven attributes are not foreseen for objectified relationships.

Geometry Use Definitions

This objectified relationship does not carry additional geometry - there is no geometry use definition.

Class IfcSite

EXPRESS Definition

Class Semantic Definition

Definition from IAI: A defined area of land, possibly covered with water, on which the project construction is to be completed. A site may be used to erect Building(s) or other AEC products.

Site may include a definition of the single geographic reference point for this site (global position using Longitude, Latitude and Elevation) for the project. This definition is given for informational purposes only; it is not intended to provide an absolute placement in relation to the world. The geometrical placement of the Site, defined by the IfcLocalPlacement is always relative to the Project if the PlacementRelTo attribute is specified.

A project may span over several connected or disconnected sites. Therefore Site Complex provides for a collection of Sites included in a project. The Site Complex is handled by an IfcGroup having a Group Purpose of 'SiteComplex'.

NOTE: This entity refers to the IFC Release 1.0 entity IfcSite, but the attribute definition has changed.

ISSUE: See issues I-125, I-194 for changes made in IFC Release 1.5.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	GenericType	Predefined generic types are specified in an enumeration. A Property Type Definition is available for each generic type.	IfcSiteTypeEnum	Building Site	Building Site	Building Site
	RefElevation	Datum elevation relative to sea level	IfcLengthMeasure	0.0	see type	0.0
	RefLongitude	World Longitude at Reference point (most likely defined in legal description). Defined as Real values for Degrees, minutes, seconds.	IfcCompoundPlaneAngleMeasure	0.0	see type	0.0
	RefLatitude	World Latitude at Reference point (most likely defined in legal description). Defined as Real values for Degrees, minutes, seconds.	IfcCompoundPlaneAngleMeasure	0.0	see type	0.0
OPT	calcSitePerimeter	Perimeter of the Site boundary. Exposed as attribute in file-based exchange.	IfcPositiveLengthMeasure	0.0	see type	0.0
OPT	calcSiteArea	Gross area for this site (horizontal projections). Exposed as attribute in file-based exchange.	IfcAreaMeasure	0.0	see type	0.0

Formal Propositions:

WR41	There shall be exactly one instance of the IfcRelContains objectified relationship that defines a ProjectContainer, i.e. referencing an IfcProject to contain this instance of IfcSite.

Informal Propositions

IR1	Products being contained by IfcSite using the IfcRelContains objectified relationship shall be either Buildings, Building Storeys, Spaces or Elements.

Interface Definitions

• I_Site

Runtime Type Definitions

Geometry Use Definitions

The geometric representation of IfcSite is given by the IfcProductShape and IfcLocalPlacement allowing multiple geometric representations. Included are:

Local Placement

The Reference Geometry for IfcSite is defined in its supertype IfcProduct. It is defined by the

• IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations. The PlacementRelTo relationship of IfcLocalPlacement shall point to the IfcProject, if relative placement is used for this Building.

Standard Geometric Representation

The standard geometric representation of IfcSite is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation of the site contour.

Currently, the usage of attribute driven geometry for IfcSite is not supported.

Advanced Geometric Representation

The advanced geometric representation of IfcSite is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for standard representation of the site contour.

Currently, the usage of attribute driven geometry for IfcSite is not supported.

Arbitrary Geometric Representation

The arbitrary geometric representation of IfcSite is defined using explicit geometry. The faceted B-Rep capabilities (with or without voids) shall be supported for arbitrary representation.

Currently, there is no difference in the usage of standard, advanced or arbitrary geometric representations for IfcSite.

Class IfcSpace

EXPRESS Definition

Class Semantic Definition

Definition from IAI: A Space represents an area or volume bounded actually or theoretically. Spaces are areas or volumes that provide for certain functions within a building.

NOTE: This entity refers to IFC Release 1.0 entity IfcSpace, however the exit path information has been excluded at this level.

ISSUE: See issue I-119, I-193 for changes made in IFC Release 1.5.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
	GenericType	Predefined generic types are specified in an enumeration. A Property Type Definition is available for each generic type.	IfcSpaceTypeEnum	Occupied Space	Circulation Space	Occupied Space
	BoundedBy	Reference to Set of Space Boundaries that defines the physical or virtual delimitation of that Space.	List[1:?] OF IfcSpaceBoundary	n/a	n/a	n/a
OPT	calcTotalPerimeter	Total Gross (physical) Perimeter of that Space. Exposed as an attribute by file-based exchange.	IfcPositiveLengthMeasure	0.0	see type	0.0
OPT	calcTotalArea	Total Gross (physical) Area of the floor level of that Space. Exposed as an attribute by file-based exchange.	IfcAreaMeasure	0.0	see type	0.0
OPT	calcTotalVolume	Total Gross (physical) Volume of that Space. Exposed as an attribute by file-based exchange.	IfcVolumeMeasure	0.0	see type	0.0
OPT	calcAverageHeight	Average Height of the space as calculated by the sending system.	IfcPositiveLengthMeasure	0.0	see type	0.0
INV	IsAssemblyThrough	Reference to the assembly relationship that creates spaces that are assemblies. It defines via the RelatingObject side this Space as the assembly of other Spaces.	SET [0:1] OF IfcRelAssemblesSpaces	n/a	n/a	NIL
INV	PartOfAssembly	Reference to the assemble relationship, that creates space assembly in which the actual space is defined as a partial space.	SET [0:1] OF IfcRelAssemblesSpaces	n/a	n/a	NIL

Formal Propositions:

WR51	The Type Defined Property for Space shall have IfcSpace as TypedClass attribute value.
WR52	There shall be exactly one instance of the IfcRelContains objectified relationship that defines a ProjectContainer, i.e. referencing an IfcProject to contain this instance of IfcSpace.
WR53	The allowed subtypes of IfcProduct that can act as space containers are: IfcSite and IfcBuildingStorey. NOTE: This rule replaces the former SELECT type IfcSpaceContainer. There shall be only one instance of the IfcRelContains objectified relationship that contains (ContainedOrReferenced = TRUE) this instance of IfcSpace. The relationship type shall therefore be either SiteContainer, or BuildingStoreyContainer.

Interface Definitions

• I_Space

Runtime Type Definitions