 | Alignment |
| Item | SPF | XML | Change | Description | IFC4x1 Final 4.1.0.0 |
|---|---|---|---|---|
| IfcAlignment | ADDED | IFC4x2 Candidate 4.2.0.0 | ||
| IfcAlignment | ||||
| PositionedRelativeTo | ADDED | |||
| Positions | ADDED | IFC4x1 Final 4.1.0.0 | ||
| IfcAlignment | ADDED | IFC4x2 Candidate 4.2.0.0 | ||
| IfcAlignment | ||||
| PositionedRelativeTo | ADDED | |||
| Positions | ADDED | IFC4x2 to IFC4x3_RC1 | ||
| IfcAlignment | ||||
| ReferencedInStructures | ADDED |
An alignment is used to define a reference system to position elements mainly for linear construction works, such as roads, rails, bridges, and others. The relative positioning along the alignment is defined by the linear referencing methodology.
NOTE See ISO 19148 Geographic information – Linear referencing for general definitions about linear referencing.
A single alignment may have:
* a horizontal alignment defined in the x/y plane of the engineering coordinate system
* an accompanying vertical alignment, defined along the horizontal alignment in the distance along / z coordinate space
* a relative alignment, defined as a span within another alignment and/or at constant or variable offsets
* a 3D alignment, either computed from the horizontal and vertical alignment, or extracted from geospatial data.
Alignments may be aggregated into referents (IfcReferent) or derivative alignments. Derivative alignments may be used to indicate dependent alignments, such as an alignment for a bridge that is relative to a parent alignment for a road, where the child IfcAlignment may have Axis set to IfcOffsetCurveByDistances that starts and ends at a span within the extent of the IfcAlignmentCurve defined at the Axis of the parent IfcAlignment.
Alignments may be assigned to groups using IfcRelAssignsToGroup, where IfcGroup or subtypes may capture information common to multiple alignments.
Supported representations of IfcAlignment.Axis are:
* IfcAlignmentCurve as a 3D horizontal and vertical alignment (represented by their alignment segments)
* IfcAlignmentCurve as a 2D horizontal alignment (represented by its horizontal alignment segments) without a vertical alignment
* IfcOffsetCurveByDistances as a 2D or 3D curve defined relative to an IfcAlignmentCurve or another IfcOffsetCurveByDistances
* IfcPolyline as a 3D alignment by a 3D polyline representation (such as coming from a survey)
* IfcPolyline as a 2D horizontal alignment by a 2D polyline representation (such as in very early planning phases or as a map representation)
NOTE Although Axis is an IfcCurve base type, only derived types IfcAlignmentCurve, IfcOffsetCurveByDistances, and IfcPolyline are meant to be supported types. Derivative specifications (Model View Definitions) may expand this set to include additional curve types.
| # | Attribute | Type | Cardinality | Description | G |
|---|---|---|---|---|---|
| 9 | PredefinedType | IfcAlignmentTypeEnum | ? | X |
| # | Attribute | Type | Cardinality | Description | G |
|---|---|---|---|---|---|
| IfcRoot | |||||
| 1 | GlobalId | IfcGloballyUniqueId | Assignment of a globally unique identifier within the entire software world. | X | |
| 2 | OwnerHistory | 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. | X |
| 3 | Name | 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. | X |
| 4 | Description | IfcText | ? | Optional description, provided for exchanging informative comments. | X |
| IfcObjectDefinition | |||||
| HasAssignments | IfcRelAssigns @RelatedObjects | S[0:?] | 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. | X | |
| Nests | IfcRelNests @RelatedObjects | S[0:1] | 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. | X | |
| IsNestedBy | IfcRelNests @RelatingObject | S[0:?] | 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. | X | |
| HasContext | IfcRelDeclares @RelatedDefinitions | S[0:1] | 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. | X | |
| IsDecomposedBy | IfcRelAggregates @RelatingObject | S[0:?] | 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. | X | |
| Decomposes | IfcRelAggregates @RelatedObjects | S[0:1] | 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. | X | |
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | 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. | X | |
| IfcObject | |||||
| 5 | ObjectType | 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. | X |
| IsDeclaredBy | IfcRelDefinesByObject @RelatedObjects | S[0:1] | 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. | X | |
| Declares | IfcRelDefinesByObject @RelatingObject | S[0:?] | 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. | X | |
| IsTypedBy | IfcRelDefinesByType @RelatedObjects | S[0:1] | 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. | X | |
| IsDefinedBy | IfcRelDefinesByProperties @RelatedObjects | S[0:?] | 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. | X | |
| IfcProduct | |||||
| 6 | ObjectPlacement | 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. | X |
| 7 | Representation | 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. | X |
| ReferencedBy | IfcRelAssignsToProduct @RelatingProduct | S[0:?] | Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product. | X | |
| PositionedRelativeTo | IfcRelPositions @RelatedProducts | S[0:1] | X | ||
| ReferencedInStructures | IfcRelReferencedInSpatialStructure @RelatedElements | S[0:?] | X | ||
| IfcPositioningElement | |||||
| ContainedInStructure | IfcRelContainedInSpatialStructure @RelatedElements | S[0:1] | Relationship to a spatial structure element, to which the positioning element is primarily associated.
IFC2x CHANGE The inverse relationship has been added to IfcGrid with upward compatibility IFC4 CHANGE The inverse relationship has been promoted from IfcGrid to this new supertype with upward compatibility | X | |
| Positions | IfcRelPositions @RelatingPositioningElement | S[0:?] | X | ||
| IfcLinearPositioningElement | |||||
| 8 | Axis | IfcCurve | The curve to be used for positioning. | X | |
| IfcAlignment | |||||
| 9 | PredefinedType | IfcAlignmentTypeEnum | ? | X | |
Instance diagram
<?xml version="1.0" encoding="utf-8"?>
<ConceptRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" uuid="733a949d-1cc8-4d40-bd6a-3836e3c195dd" name="IfcAlignment" applicableRootEntity="IfcAlignment">
<Applicability>
<Template ref="425ea152-03b9-4561-a5c8-8bc3b50f9289" />
<TemplateRules operator="and">
</TemplateRules>
</Applicability>
<Concepts>
<Concept uuid="d0249472-003e-4fc6-a663-6d8d44069c31" name="Alignment Attributes">
<Template ref="48afbff3-893b-4791-94dd-fface6eac658" />
</Concept>
</Concepts>
</ConceptRoot>
| # | Concept | Template | Model View |
|---|---|---|---|
| IfcRoot | |||
| Identity | Software Identity | General Usage | |
| Revision Control | Revision Control | General Usage | |
| IfcObjectDefinition | |||
| Classification Association | Classification Association | General Usage | |
| IfcObject | |||
| Object User Identity | Object User Identity | General Usage | |
| Object Predefined Type | Object Predefined Type | General Usage | |
| Object Typing | Object Typing | General Usage | |
| Property Sets for Objects | Property Sets for Objects | General Usage | |
| Property Sets with Override | Property Sets with Override | General Usage | |
| IfcProduct | |||
| Product Placement | Product Placement | General Usage | |
| Product Geometric Representation | Product Geometric Representation | General Usage | |
| IfcPositioningElement | |||
| Placement | Product Local Placement | General Usage | |
| Footprint Geometry | FootPrint Geometry | General Usage | |
| IfcAlignment | |||
| Alignment Attributes | Alignment Attributes | General Usage | |
<xs:element name="IfcAlignment" type="ifc:IfcAlignment" substitutionGroup="ifc:IfcLinearPositioningElement" nillable="true"/>
<xs:complexType name="IfcAlignment">
<xs:complexContent>
<xs:extension base="ifc:IfcLinearPositioningElement">
<xs:attribute name="PredefinedType" type="ifc:IfcAlignmentTypeEnum" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
ENTITY IfcAlignment
SUBTYPE OF (IfcLinearPositioningElement);
PredefinedType : OPTIONAL IfcAlignmentTypeEnum;
END_ENTITY;
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