IFC Guide

Kapitola 03:	PROJECT CONTAINER ELEMENT AND BASE SETTINGS	html	pdf orig
Kapitola 04:	SPATIAL STRUCTURE AND SPACE ELEMENTS	html	pdf orig
Kapitola 05:	BUILDING ELEMENTS	html	pdf orig
Kapitola 06:	BUILDING SERVICES ELEMENTS AND RELATED CONCEPTS	html	pdf orig
Kapitola 09:	SHAPE REPRESENTATION OF ELEMENTS	html	pdf orig
Kapitola 10:	PROPERTIES OF ELEMENTS	html	pdf orig

Obsah kapitoly

4.1 COMMON CONCEPTS FOR ALL SPATIAL STRUCTURE ELEMENTS
4.2 BUILDING THE SPATIAL STRUCTURE
4.2.1 Site
4.2.2 Building
4.2.3 Building Story
4.2.3.1 Story elevation
4.2.4 Space
4.2.4.1 Space boundaries
4.2.5 Concept of Zone
4.2.5.1 Zone Naming

4 Spatial structure and space elements

All spatial structure elements inherit the concepts associated to products, which are provided by IfcProduct. It includes:

„Identification“ and „Change Management“, see section 3.1.
„Generic Type Assignment“ and „Generic Property Attachment“, see section 9.2.
„External References“ to documents, classifications and libraries, see section 10.4.
„Generic Decomposition“ redefined as decomposition of the spatial structure within this section.
„Placement“ and „Shape Representation“, see section 9, refined as spatial structure element specific shape representation (also referred to as geometry use cases) within this section.
„Element in Space Containment“, introduced within this section.
„Element Quantities“, see section 10.3.

4.1 Common concepts for all spatial structure elements

The spatial structure can be defined as „breakdown of the project model into manageable subsets according to spatial arrangements“. It should be noted, that other decomposition structures for a project exist, but that the spatial structure is common to most disciplines and design tasks. It is therefore seen as the primary structure for building projects and required for the data exchange. The following four different concepts are subsumed under the IfcSpatialStructureElement entity:

Project (uppermost container of all information)
Site (also site complex and part of site)
Building (also building complex and building section)
Building story (also partial building story)
Space (also partial space)

Figure 6 : Definition of spatial structure elements

These different entities are contained by each other such as they provide a clear hierarchical structure for the building project. The next figure shows such a structure.

Figure 7 : Spatial structure of a building project

The four subtypes IfcSite, IfcBuilding, IfcBuildingStorey, IfcSpace are used to represent the levels of the spatial structure. Each has

a name (by IfcRoot.Name)
a description (by IfcRoot.Description)
a long name

The Name attribute has to be used to store the name of the building, and building story. E.g., the story name, such as “First Floor” should be exchanged by Name.

#9=IFCBUILDINGSTOREY(‚abcdefghijklmnopqrs109‘, #109, ‚First Floor‘, $, $, $, $, $,.ELEMENT., $);

The various subtypes define further attributes, which are introduced in the appropriate sub sections. In total each of the subtypes inherit the following attributes and inverse relationships:

ENTITY IfcSpatialStructureElement
GlobalId : IfcGloballyUniqueId;
OwnerHistory : IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ObjectType : OPTIONAL IfcLabel;
ObjectPlacement : OPTIONAL IfcObjectPlacement;
Representation : OPTIONAL IfcProductRepresentation;
LongName : OPTIONAL IfcIdentifier;
CompositionType : IfcElementCompositionEnum;
INVERSE
IsDefinedBy : SET OF IfcRelDefines;
HasAssociations : SET OF IfcRelAssociates;
HasAssignments : SET OF IfcRelAssigns;
Decomposes : SET OF IfcRelDecomposes;
IsDecomposedBy : SET [0:1] OF IfcRelDecomposes;
ReferencedBy : SET OF IfcRelAssignsToProduct;
ContainsElements : SET OF IfcRelContainedInSpatialStructure;
END_ENTITY;

4.2 Building the spatial structure

The spatial structure of a building project is created by using the fundamental decomposition relationship.

The subtype IfcRelAggregates is used to link the instances of IfcProject, IfcSite, IfcBuilding, IfcBuildingStorey, IfcSpace (provided that all levels are applicable) and establishes an hierarchical structure.

Figure 8 : Mandatory and optional levels of the spatial structure

Whereas the IfcProject, IfcBuilding and IfcBuildingStorey are mandatory levels for the exchange of complex project data, the IfcSite and IfcSpace represent optional levels (which may be provided, if they contain necessary data, but don't need to be provided).

In order to define a complex or a partial spatial structure element, the CompositionType attribute is used. If the CompositionType is COMPLEX, then it defines a site complex, or a building complex. If the CompositionType is PARTIAL, then it defines a partial site or a building section. If the CompositionType is ELEMENT, it defines (just) the site or the building.

Each instance of IfcProject, IfcSite, IfcBuilding, IfcBuildingStorey, IfcSpace is connected to other instances of the spatial structure by an instance of IfcRelAggregates, where the single RelatingElement points to the element at the higher level and the 1 to many RelatedElements point to the elements at the lower level of the hierarchy.

Figure 9 : Decomposition of a spatial structure

Note: The Figure 8 shows the use of the IfcRelAggregates to define a spatial structure of a building project having a single site with one building. The building is further divided into two building section. Two stories are assigned to the first building section and three stories are assigned to the second building section.

The Figure 8 shows a vertical and horizontal division of the building. In these cases, the horizontal division (into building sections) takes priority and the building stories are later assigned to the sections. A building story that physically spans through two building sections would therefore be subdivided into two building stories, and each then assigned to a single building section. Figure 9 shows a graphical image of the sample spatial structure.

Figure 10 : Layout of the example spatial structure

The example file shows the basic spatial structure of the example shown in Figure 8 and Figure 9. It should be noted, that the following information has to be given for each project:

the Name (enforced by where rule: WR1)
at least one RepresentationContexts, being an IfcRepresentationContext (or subtype)
the UnitsInContext to define the global units

#1=IFCPROJECT('abcdefghijklmnopqrs101', #101, 'sample project', $, $, $, $, (#1000), #1010);
#3=IFCSITE('abcdefghijklmnopqrs103', #103, $, $, $, $, $, $, .ELEMENT., $, $, $, $, $);
#4=IFCBUILDING('abcdefghijklmnopqrs104', #104, $, $, $, $, $, $, .ELEMENT., $, $, $);
#6=IFCBUILDING('abcdefghijklmnopqrs106', #106, $, $, $, $, $, $, .PARTIAL., $, $, $);
#7=IFCBUILDING('abcdefghijklmnopqrs107', #107, $, $, $, $, $, $, .PARTIAL., $, $, $);
#8=IFCBUILDINGSTOREY('abcdefghijklmnopqrs108', #108, $, $, $, $, $, $, .ELEMENT., $);
#9=IFCBUILDINGSTOREY('abcdefghijklmnopqrs109', #109, $, $, $, $, $, $, .ELEMENT., $);
#21=IFCBUILDINGSTOREY('abcdefghijklmnopqrs121', #121, $, $, $, $, $, $, .ELEMENT., $);
#22=IFCBUILDINGSTOREY('abcdefghijklmnopqrs122', #122, $, $, $, $, $, $, .ELEMENT., $);
#23=IFCBUILDINGSTOREY('abcdefghijklmnopqrs123', #123, $, $, $, $, $, $, .ELEMENT., $);
#10=IFCRELAGGREGATES('abcdefghijklmnopqrs110', #110, $, $, #1, (#3));
#11=IFCRELAGGREGATES('abcdefghijklmnopqrs111', #111, $, $, #3, (#4));
#12=IFCRELAGGREGATES('abcdefghijklmnopqrs112', #112, $, $, #4, (#6, #7));
#13=IFCRELAGGREGATES('abcdefghijklmnopqrs113', #113, $, $, #6, (#8, #9));
#14=IFCRELAGGREGATES('abcdefghijklmnopqrs114', #114, $, $, #7, (#21, #22, #23));

4.2.1 Site

The site, represented by IfcSite, is used to provide additional information about the building site and may include the representation of the terrain model for the building site. The following additional information (to the inherited Name, Description, LongName and ObjectType) may be given for an IfcSite.

the RefLatitude, RefLongitude, RefElevation to provide the world latitude, longitude and datum elevation of a reference point within the site. That information is given for information purposes and may be used within thermal or other applications,
the LandTitleNumber which is used by many constituencies to identify the site,
the SiteAddress, which is for information purposes only, but may be exchanged together with the virtual building model

In addition to the alphanumerical attributes the site mainly handles the reference to the building(s) which is(are) built or maintained at that site and the geometry of the terrain. Three different shape representations can be exchanged for the IfcSite:

1. the set of survey points and optionally breaklines, this is normally the outcome from the survey at the site and similar to existing simple exchange formats for site or terrain geometry. In this case the triangulation of the resulting face or shell based geometry (or mesh) is left to the receiving application.

2. the mesh of the terrain model, a set of 3 or 4 side faces connected in an connected face set, in this case the triangulation is already provided by the sending application

3. the b-rep geometry of the resulting solid (requires a fully closed solid for the terrain) In case 1 the following applies to the IfcShapeRepresentation used (see Figure 10):

the RepresentationIdentifier should be “SurveyPoints”;
the RepresentationType “GeometricSet”;
the Items should include an IfcGeometricSet containing all survey points as 3D IfcCartesianPoint and the breaklines as IfcPolyline connecting the selected survey points.

Figure 11 : site representation by survey points and breaklines

In case 2 the following applies to the IfcShapeRepresentation used (see Figure 11):

the RepresentationIdentifier should be “Mesh”;
the RepresentationType “SurfaceModel'”;
the Items should include an IfcFaceBasedSurfaceModel containing one or many IfcConnectedFaceSet with the triangulated (or quadrilateral and co-planer) faces as IfcFace.

Figure 12 : site representation by a mesh

In case 3 the following applies to the IfcShapeRepresentation used:

the RepresentationIdentifier should be “Body”;
the RepresentationType “Brep”;
the Items should include an IfcFacetedBrep or an IfcFacetedBrepWithVoids (following the general rules for B-rep Geometry (see 9.1.4.1.4.1).

4.2.2 Building

The building, represented by IfcBuilding, is used to provide additional information about the building itself. It is associated (if given) to an IfcSite, if not, than directly to the IfcProject.

A building includes the references to the building stories which belong to that building, or a building may have building sections, which would be referenced by the building, in that case the building stories are referenced by the building sections⁴

The following additional information (in addition to the inherited Name, Description, LongName and ObjectType) may be given for an IfcBuilding.

the ElevationOfRefHeight which is needed to put the elevation datum of the stories into the global context of the elevation above sea level. The ElevationOfRefHeight gives the height relative to ± 0.00 (normally the elevation of the ground floor). Although not strictly required this information should be exchange if specified by the user in the source application.
the ElevationOfTerrain gives the minimum elevation of the terrain at the foot print of the building, this is for information purposes only and may not be sufficient when the building is situated in a sloped terrain. In that case only the terrain model, associated to IfcSite, can provide this information geometrically.
the BuildingAddress which is for information purposes only, but may be exchanged together with the virtual building model. It may, or may not, be identical with IfcSite.SiteAddress.

Usually the building does not contain its own shape representations, as it is provided by its constituting elements. The ObjectType attribute should be reserved to contain a simple type description of the building (following local building standards), if a more complex classification of the building is required, the proper classification resource should be used (see 10.4.2).

The example below describes a sample building structure with building specific information (name, type, long name and address given). Also note that unit assignment has mm as length unit (not shown), therefore elevation is given in mm. PS: No position is given in the example.

4.2.3 Building Story

The building story, represented by IfcBuildingStorey, is used to provide the information about the building story itself, a vertical structure normally used within building and construction. It is always associated to an IfcBuilding, either the building or the building section.

A building story includes the references to the spaces which belong to that building story. A building story may have partial building stories (such as split levels), which would be referenced by the building story, in that case the spaces are referenced by the partial building stories⁵

The following additional information (in addition to the inherited Name, Description, LongName and ObjectType) may be given for an IfcBuildingStorey.

the Elevation which is needed to identify the datum of the story (based on the raw construction of the slab), although the attribute is optional, it is necessary for many exchange scenarios (or views)

Note⁴
It should be noted that the creation and exchange of such complex spatial structures (such as building sections) may be beyond current capabilities of software systems used in building/construction.

Note⁵
It should be noted that the creation and exchange of such complex spatial structures(such as split level stories within normal stories) may be beyond current capabilities of software systems used in building/construction.

Usually the building story does not contain its own shape representations, as it is provided by its constituting elements. The ObjectType attribute should be reserved to contain a simple type description of the building story.

Such a description should be agreed on in a project or local context and may include identifiers as „Basement“, „GroundFloor“, „UpperFloor“, or „RoofTop“.

Figure 13 : Example of building story structure

The example below describes the building structure, as given in Figure 12, including all relative placements (see 9.1.2.1.1) and attributes as discussed.

#1=IFCPROJECT('abcdefghijklmnopqrs101', #101, 'sample project', $, $, $, $, (#1000), #1010);
#3=IFCSITE('abcdefghijklmnopqrs103', #103, $, $, $, #1500, $, $, .ELEMENT., $, $, $, $, $);
#4=IFCBUILDING('abcdefghijklmnopqrs104', #104, 'sample building', $, 'office', #1501, $, 'sample building at 100 main road', .ELEMENT., 129350., 128750., #1020);
#6=IFCBUILDINGSTOREY('abcdefghijklmnopqrs106', #106, 'basement story', $, 'Basement', #1502, $, $, .ELEMENT., -2600.);
#7=IFCBUILDINGSTOREY('abcdefghijklmnopqrs107', #107, '1st story', $, 'GroundFloor', #1503, $, $, .ELEMENT., 0.);
#8=IFCBUILDINGSTOREY('abcdefghijklmnopqrs108', #108, '2nd story', $, 'UpperFloor', #1504, $, $, .ELEMENT., 2800.);
#9=IFCBUILDINGSTOREY('abcdefghijklmnopqrs109', #109, 'walkable rooftop', $, 'RoofTop', #1505, $, $, .ELEMENT., 5600.);
#10=IFCRELAGGREGATES('abcdefghijklmnopqrs110', #110, $, $, #1, (#3));
#11=IFCRELAGGREGATES('abcdefghijklmnopqrs111', #111, $, $, #3, (#4));
#13=IFCRELAGGREGATES('abcdefghijklmnopqrs113', #113, $, $, #4, (#6, #7, #8, #9));
#1500=IFCLOCALPLACEMENT($,#1600);
#1501=IFCLOCALPLACEMENT(#1500,#1601);
#1502=IFCLOCALPLACEMENT(#1501,#1602);
#1503=IFCLOCALPLACEMENT(#1501,#1603);
#1504=IFCLOCALPLACEMENT(#1501,#1604);
#1505=IFCLOCALPLACEMENT(#1501,#1605);
#1600=IFCAXIS2PLACEMENT3D(#1700,$,$);
#1601=IFCAXIS2PLACEMENT3D(#1701,$,$);
#1602=IFCAXIS2PLACEMENT3D(#1702,$,$);
#1603=IFCAXIS2PLACEMENT3D(#1703,$,$);
#1604=IFCAXIS2PLACEMENT3D(#1704,$,$);
#1605=IFCAXIS2PLACEMENT3D(#1705,$,$);
#1700=IFCCARTESIANPOINT((0.,0.,0.));
#1701=IFCCARTESIANPOINT((0.,0.,0.));
#1702=IFCCARTESIANPOINT((0.,0.,-2600.));
#1703=IFCCARTESIANPOINT((0.,0.,0.));
#1704=IFCCARTESIANPOINT((0.,0.,2800.));
#1705=IFCCARTESIANPOINT((0.,0.,5600.));

Beside spaces normally all building elements are assigned to the building story, in which they are located. If building elements (or spaces) span through many stories, they are assigned to the story at which they are based.
Also elements that are linked to other elements, such as openings or doors and windows are separately assigned directly to the building story.

This containment relationship is handled by the UoF „Element in Space Containment“. The relationship IfcRelContainsInSpatialStructure should be used to exchange it.

The spatial structure is also reflected in the relative positioning. Each story, building and site should declare its own object coordinate system, which is positioned relative to the coordinate system of the spatial structure at the next higher level (i.e. identical with the RelatingObject in the IfcRelAggregates containment relationship)^6.

Figure 14 : relative object placement of the spatial structure

4.2.3.1 Story elevation

There are two scenarios for exporting multi-story buildings using the relative object placement and the Elevation attribute. These apply particularly to the coordination view of IFC2×.

Figure 15 : Story elevation with relative placement

Note⁶
The relative placement can be omitted if only absolute placements (see 10.1.2.1.2) are used.

the default scenario (to be used whenever possible) requires the use of relative object placements (as shown in Figure 14) and the use of the Elevation attribute.
in this case the first story of the previous example (#8) needs to have a relative local placement (usually relative to IfcBuilding) with the z-coordinate of the placement location being equal to the story elevation (here “2800.”) and the Elevation attribute set to the elevation (again “2800.”).
all building elements, that are assigned to the building story are place relative to the building story, i.e. most walls would usually have a local placement with the z- coordinate of the placement location being “0.00”.
the fallback scenario (to be used when it is the user intention not to place stories on top of each other) uses of relative object placements without using the z-coordinate of the placement location but requires the use of the Elevation attribute, see Figure 15.
in this case the first story of the previous example (#8) is allowed to have a relative local placement (usually relative to IfcBuilding) with the z-coordinate of the placement location being equal to the building (here “0.”) but the Elevation attribute has to be set to the elevation (here “2800.”).
all building elements, that are assigned to the building story are place relative to the building story, but as it is set to equal height to the building, most walls would now usually have a local placement with the z-coordinate of the placement location being “2800.”.

Figure 16 : Story elevation with placement height zero and elevation

4.2.4 Space

The space, represented by IfcSpace, is used to provide all information about the space as a functional area or volume within a spatial structure. It is associated (if given) to an IfcBuildingStorey, in the special case of an outdoor space, however, it can be directly associate to an IfcSite.

The following guidelines should apply for using the Name, Description, LongName and ObjectType attributes.

the Name holds the unique name (or space number) from the plan.
the Description holds any additional information field the user may have specified, there are no further recommendations.
the LongName holds the full name of the space, it is often used in addition to the Name, if a number is assigned to the room, than the descriptive name is exchanged as LongName.
the ObjectType holds the space type, i.e. usually the functional category of the space7

Note⁷ This can only be a rough indication of the type, for proper classification according to a building code the light weight classification (see 11.4.2.7.1) should be used.

Figure 17 : room stamp with space information The following partial file contains the snip-out of the space object with all name and simple type information, here in a German context8.

#285=IFCSPACE('3LweZaMsz0nR$8x1w5Bjie', #6, 'W-001', $, 'Wohnen und Aufenthalt', #284,
#300, 'Elternschlafzimmer', .ELEMENT., .INTERNAL., 0.0);

The following additional information (in addition to the inherited Name, Description, LongName and ObjectType) may be given for an IfcSpace.

the InteriorOrExteriorSpace which is an enumeration, indicating whether the space is an internal space (i.e. fully enclosed by a building structure) or an external space,
the ElevationWithFlooring which is needed to identify the datum of the finish of the space (based on the flooring on top of the raw construction of the slab).

Spaces normally contain all building service or interior design elements (such as distribution elements, electrical elements, furniture, fixture and equipment), if they are located within a single space. Large distribution elements, such as ducts or pipes, which span through multiple spaces can only be contained by the building story. This containment relationship is handled by the UoF „Element in Space Containment“. The relationship IfcRelContainsInSpatialStructure should be used to exchange it.

If the classification of the space should be exchanged explicitly it should follow the UoF “external classification association”, particularly the “light weight classification” (see 10.4.2.7.1).

Taking the previous example, the space is classified according to the German DIN277 as a HNF1. It should be exchanged as follows:

#285=IFCSPACE(‚3LweZaMsz0nR$8×1w5Bjie‘, #6, ‚W-001‘, $, ‚Wohnen und Aufenthalt‘, #284, #300, ‚Elternschlafzimmer‘, .ELEMENT., .INTERNAL., 0.0); #301=IFCCLASSIFICATIONREFERENCE($, ‚HNF1‘, ‚Wohnen und Aufenthalt‘, #302); #302=IFCCLASSIFICATION(‚Deutsche Industrienorm‘, ‚Juni 1987‘, $, ‚DIN277‘); #303=IFCRELASSOCIATESCLASSIFICATION(‚2hJ0MTr$v9hgPt_3AR_yCZ‘, #6, $, $, (#285), #301);

If the quantities should be exchanged explicitly it should follow the UoF “„Element Quantities“ (see 10.3).
Quantities of spaces normally include net or gross areas, volumes and perimeters. They are normally calculated according to a Method of Measurement, which has to be given as well in order to interpret the results.

The following Figure 17 shows the quantities of the example space. They are all measured according to the Method of Measurement DIN277.

Note⁸: English translation of the example: type is living area and long name is master’s bedroom. Elevation with flooring is 0.0, i.e. the finish of the ground level.

Figure 18 : Quantities of sample space

The exchange of the calculated values for area and volume should be done by using the IfcElementQuantity holding the Method of Measurement and the individual subtypes of IfcPhysicalQuantity for each value.
Since the Unit attribute is NIL, the globally defined units apply to the values of the quantity measures.

#285=IFCSPACE('3LweZaMsz0nR$8x1w5Bjie', #6, 'W-001', $, 'Wohnen und Aufenthalt', #284, #300, 'Elternschlafzimmer', .ELEMENT., .INTERNAL., 0.);
#304=IFCELEMENTQUANTITY('2hJ0MTr$v9hgPt_3AR_yDZ', #6, 'Space Quantities', $, 'DIN277', (#306,#305));
#305=IFCQUANTITYAREA('HNF1', 'Net area', $, 58.29);
#306=IFCQUANTITYVOLUME('NRI a', 'Net volume', $, 157.39);
#307=IFCRELDEFINESBYPROPERTIES('2hJ0MTr$v9hgPt_3AR_yEZ', #6, $, $, (#285), #304);
#7=IFCSIUNIT(*, .LENGTHUNIT., $, .METRE.);
#8=IFCSIUNIT(*, .AREAUNIT., $, .SQUARE_METRE.);
#9=IFCSIUNIT(*, .VOLUMEUNIT., $, .CUBIC_METRE.);
#10=IFCSIUNIT(*, .MASSUNIT., $, .GRAM.);
#11=IFCSIUNIT(*, .TIMEUNIT., $, .SECOND.);
#12=IFCSIUNIT(*, .THERMODYNAMICTEMPERATUREUNIT., $, .DEGREE_CELSIUS.);
#13=IFCSIUNIT(*, .LUMINOUSINTENSITYUNIT., $, .LUMEN.);
#14=IFCUNITASSIGNMENT((#7,#8,#9,#10,#11,#12,#13));

In addition to the alphanumerical attributes the space mainly holds the room geometry. Three different shape representations can be exchanged for the IfcSpace:

the footprint of the space – a 2D closed polyline or composite curve.
the 3D shape of the shape – a 3D body defined by extruding the footprint and potentially clipping the result.
the b-rep geometry to capture any 3D shape of spaces.

In case 1 the following applies to the IfcShapeRepresentation used:

the RepresentationIdentifier should be ‚FootPrint‘;
the RepresentationType should be ‚Curve2D‘, or ‚GeometricCurveSet‘;
the Items should include an IfcCurve, normally IfcCompositeCurve for any curve, or IfcPolyline for curves with only line segments.

Within the simple space example used in Figure 18 the shape presentation of the footprint is given by a polyline, as no arc segments are used.

NOTE: If a space has inner boundaries (i.e. subtraction areas) the RepresentationType should be ‚GeometricCurveSet‘, allowing a set of Items to store the outer and inner boundaries.

Figure 19 : footprint geometry of the sample space

In case 2 the following applies to the IfcShapeRepresentation used:

the RepresentationIdentifier should be ‚Body‘;
the RepresentationType should be ‚SweptSolid‘ (or ‘Clipping’);
the Items should include an IfcExtrudedAreaSolid, normally having the SweptArea being an IfcArbitraryClosedProfileDef.

Within the simple space example used in Figure 18 (having a height of 2.7m) the shape presentation of the body is given by an extruded solid based on an arbitrary profile without voids.

#285=IFCSPACE('3LweZaMsz0nR$8x1w5Bjie', #6, 'W-001', $, 'Wohnen und Aufenthalt', #284, #300, 'Elternschlafzimmer', .ELEMENT., .INTERNAL., 0.);
#300=IFCPRODUCTDEFINITIONSHAPE($, $, (#500));
#500=IFCSHAPEREPRESENTATION (#70, 'Body', 'SweptSolid', (#501));
#501=IFCEXTRUDEDAREASOLID (#503, #502, #509, 2.7);
#502=IFCAXIS2PLACEMENT3D (#510, $, $);
#503=IFCARBITRARYCLOSEDPROFILEDEF (.AREA., $, #504);
#504=IFCPOLYLINE ((#505, #506, #507, #508, #505));
#505=IFCCARTESIANPOINT ((0., 0.));
#506=IFCCARTESIANPOINT ((7.635, 0.));
#507=IFCCARTESIANPOINT ((7.635, -7.635));
#508=IFCCARTESIANPOINT ((0., -7.635));
#509=IFCDIRECTION ((0., 0., 1.));
#510=IFCCARTESIANPOINT ((0., 0., 0.));

In case 3 the following applies to the IfcShapeRepresentation used:

the RepresentationIdentifier should be ‚Body‘;
the RepresentationType should be ‘Brep’;
the Items should include an IfcFacetedBrep, (with or without voids).

4.2.4.1 Space boundaries

The space boundaries define the relationship between a space and its bounding elements. Each space boundary defines an 1:1 relationship between a space and a single bounding building element (if given), in this case a physical space boundary.
In cases of an open space, the open side is defined as a virtual space boundary.

The provision of space boundaries for spaces is declared in the UoF “Space Element Boundaries”.
Space boundaries can be defined:

logically, i.e. without a geometric representation of the boundary,
physically, i.e. with a geometric representation given by a surface definition.

If space boundaries are defined physically then the geometry is given within the object coordinate system of the space⁹.
For space boundaries defined along walls, the following geometry types should be used:

for straight walls – IfcSurfaceOfLinearExtrusion, based on an IfcArbitraryOpenProfileDef with an IfcPolyline based Curve. (also IfcTrimmedCurve based on an IfcLine segment is possible).
for curved walls – IfcSurfaceOfLinearExtrusion, based on an IfcArbitraryOpenProfileDef with an IfcTrimmedCurve based Curve.

In the simple sample space, a space boundary is defined as shown in Figure 19.

Figure 20 : space boundary of sample space

#285=IFCSPACE('3LweZaMsz0nR$8x1w5Bjie', #6, 'W-001', $, 'Wohnen und Aufenthalt', #284, #300, 'Elternschlafzimmer', .ELEMENT., .INTERNAL., 0.);
#1000=IFCWALLSTANDARDCASE('2yOJsOFC58PATD3uOMT1eh', #6, $, $, $, #1035, $, $);
#1036=IFCRELSPACEBOUNDARY('3LweZaMsz0nR$8x1w5Bklm', #6, $, $, #285, #1000, #1037, .PHYSICAL., .INTERNAL.);
#1037=IFCCONNECTIONSURFACEGEOMETRY(#1038, $);
#1038=IFCSURFACEOFLINEAREXTRUSION(#1039, #1040, #1041, 2.7);
#1039=IFCARBITRARYOPENPROFILEDEF(.CURVE., $, #1042);
#1040=IFCAXIS2PLACEMENT3D(#1045, $, $);
#1041=IFCDIRECTION((0.,0.,1.));
#1042=IFCPOLYLINE((#1043,#1044));
#1043=IFCCARTESIANPOINT((7.635,7.635));
#1044=IFCCARTESIANPOINT((0.,7.635));
#1045=IFCCARTESIANPOINT((0.,0.,0.));

4.2.5 Concept of Zone

Within the IFC Model, a zone is defined as a subtype of IfcGroup. That is, it acts as a functional related aggregation of objects.
However, whilst the IfcGroup can aggregate any set of instances that are subtypes of IfcObject, the IfcZone is restricted by a WHERE rule so that it can only aggregate spaces or other zones.

ENTITY IfcZone
SUBTYPE OF (IfcGroup);
WHERE WR1 : SIZEOF (QUERY (temp * SELF\IfcGroup.IsGroupedBy.RelatedObjects |
NOT(('IFCPRODUCTEXTENSION.IFCZONE' IN TYPEOF(temp)) OR
('IFCPRODUCTEXTENSION.IFCSPACE' IN TYPEOF(temp))) )) = 0;
END_ENTITY;

Note⁹ The provision of the space boundary is not required in all views declared for the use of the IFC2× model. However some views, like the HVAC or code-checking view depend on the provision of space boundaries.

The purpose of a zone is to be able to define spaces that are considered together for the purposes of some external requirement.
That is, spaces may be aggregated into a zone for the purposes of provision of engineering services (the maximum load on the south side of a building occurring at a different time of day to the maximum load on the north side of the building), for fire compartmentation, sprinkler zoning, security zoning, office tenancy etc.

Whilst it is normally expected that the spaces in a zone will be contiguous (i.e. adjacent to each other), this is not a mandatory requirement.
Therefore, it is possible to define a zone that includes non- adjoining spaces.
These spaces may also be on separate storeys within the building.
This is relevant for certain types of zoning that may only be applicable to particular types of space.

4.2.5.1 Zone Naming

There may be many instances of IfcZone within a building, each zone fulfilling a different purpose. To distinguish between them, it is important that each zone is named. Zone names should be defined using the inherited Name attribute from IfcRoot.
This resolves to a simple STRING data type. Note also that the attribute ObjectType inherited from IfcObject may be optionally used to qualify the zone name further.
This is particularly used in conjunction with property sets or type being attached to the zone.