The IfcPropertyTypeResource defines the basic capabilities for Property definitions that can be attached to objects and relationships. It also includes the definition of Shape Representation as a particular property.
One motivation for defining a "Type" of an Element is to establish a standard that will be used many times in a project. In these cases, a standard type is established through the definition of a set of Properties or Characteristics that will be held constant for all occurrences in the Project model. Therefore, there should be a single record of these attributes that is associated with the Type Definition object rather than with each occurrence of the element.
Another motivation for defining a "Type" of an Element is to establish a use or purpose for the element that requires a that a standard set of Properties be defined for each occurrence. In these cases, this standard set of Properties will be determined by the type, but values for these Properties will vary for each occurrence of the element type.
Those Property Definitions can be either:
The following figure gives an overview about the different usage of Properties in IFC.
This schema defines in addition the Shape Representation as an important property for IFC objects. It shall be noted that currently the Shape Representation shall not be included into a Property Set and is therefore not Type Driven.
It also defines the structure of Shape Representation that includes two general capabilities:
EXPRESS Definition
Definition from IAI: The IfcTypeDefDomainViewEnum defines the domain view under which the type definition is valid. It allows for multiple typing of objects. The Enumeration complies with the domain models defined in a certain IFC Release.
Enumeration:
CrossDomain |
Type defined in the Core or Interoperability Layer |
Architecture |
Type defined in the Domain model for Architecture |
HVAC |
Type defined in the Domain model for HVAC |
FacMgmt |
Type defined in the Domain model for Facilities Management |
NOTE: This type is new in IFC Release 1.5
ISSUE: See issue I-079 for changes made in IFC Release 1.5.
EXPRESS Definition
Definition from IAI: The IfcRepDetailTypeEnum defines the detailing view under which the Shape Representation is valid. Detailing refers to the different levels of abstraction during the various design processes. The enumeration contains the predefined detailing views for this release.
Enumeration:
Sketch |
Abstraction for conceptual design state. |
Outline |
Abstraction for early design state. |
Design |
Level of detail for design state. |
Detail |
Level of detail for detailed design state. |
Undefined |
Generic definition, the generation of the views is left to the receiving application. |
NOTE: This type is new in IFC Release 1.5
ISSUE: See issue I-049 for changes made in IFC Release 1.5.
EXPRESS Definition
Definition from IAI: The IfcRepViewTypeEnum defines the projection under which the Shape Representation is valid.
NOTE: This type is new in IFC Release 1.5. Enumeration:
Plan |
Shape Representation used for Plans |
Section |
Shape Representation used for Sections |
Elevation |
Shape Representation used for Elevations |
Isometric |
Shape Representation used for Isometric Drawings |
Diagrammatic |
Shape Representation used for Diagrammatic Presentations |
Undefined |
Generic definition, the generation of the views is left to the receiving application. |
EXPRESS Definition
Definition from IAI: The IfcShapeRepTypeEnum defines the particular type of the IfcShapeRepresentation and constrains the allowed representation items for the shape representation. Currently three shape representation types are distinguished in IFC:
NOTE: This type is new in IFC Release 1.5. Enumeration:
BoundingBox |
This shape representation represents the product shape as the bounding box. |
Standard |
This shape representation represents the standard shape representation, as defined in the geometry use section of the product. |
Advanced |
This shape representation represents the advanced shape representation, as defined in the geometry use section of the product. |
Arbitrary |
This shape representation represents the arbitrary shape representation, as defined in the geometry use section of the product. Arbitrary shape representation in IFC Release 1.5 is normally given by a faceted B-Rep representation. |
EXPRESS Definition
Definition from IAI: The IfcObjectReference defines a class, which wraps an object ID, the IfcGloballyUniqueId, by which it can reference another object from within a property set. The Descriptor names the property that is defined by the object reference.
NOTE: This is a new class in IFC Release 1.5.
ISSUE: See issue I-252 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Descriptor |
Name that uniquely defines the Property in case of type driven properties, in case of extended properties the name must be agreed upon among the parties that communicate the extension. |
STRING |
see type |
see type |
n/a |
|
ObjectReference |
Value of the globally unique ID of the reference object. |
see type |
see type |
n/a |
No formal or informal propositions defined at this level.
Class IfcOccurrencePropertySet
EXPRESS Definition
Definition from IAI: The IfcOccurrencePropertySet defines a set of type driven properties (and is therefore defined as part of the IFC standard) that have a single occurrence per instance of a semantic object, i.e. each semantic object instance creates its own instance of the IfcOccurrencePropertySet with particular property values.
NOTE: This is a new class in IFC Release 1.5.
ISSUE: See issue I-78 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
TypeReference |
Reference to the Type Definition that defines the Occurrence Property Set. |
see type |
see type |
n/a |
Formal Propositions:
WR31 |
Product Shapes shall not be included in a Type Driven Property Set. |
EXPRESS Definition
Definition from IAI: The IfcProperty is the common abstraction for all Properties, defined within the IFC Model. Those Properties can be either simple properties, complex and predefined properties or groups of properties, and Product Shapes as a particular specialization of Property.
NOTE: This is a new class in IFC Release 1.5.
ISSUE: See issue I-080, I-081, GI-002 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
INV |
PartOfPropertySet |
Reference to the IfcPropertySet, in which the IfcProperty is contained. |
Set[0:1] IfcPropertySet |
see type |
see type |
NIL |
No formal or informal propositions defined at this level.
EXPRESS Definition
Definition from IAI: The IfcPropertySet is a container class that allows the definition of collections of Properties or other Property Sets. It therefore allows for nested list. These lists may than be attached to objects or relationships at runtime. There are three general usage cases for Property Sets:
An IfcPropertySet can include other IfcPropertySet's, and it can reference its parent IfcPropertySet, in which it is included. The inherited (INV) PartOfPropertySet Relationship is used to reference the parent IfcPropertySet.
NOTE: This is an enhanced version of the IFC Release 1.0 class IfcAttributeSet.
ISSUE: See issues I-078, I-080, I-187, GI-003 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ProjectId |
Assignment of a globally unique identifier that allows to ensure uniqueness in a global context. |
see type |
see type |
n/a |
|
|
Descriptor |
Unique descriptor of the Property Set, in case of type driven Property Sets the descriptor is defined as part of the IFC standard |
STRING |
see type |
see type |
n/a |
|
HasProperties |
List of contained Properties or other Property Sets. |
List [1:?] IfcProperty |
see type |
see type |
n/a |
Formal Propositions:
WR21 |
It has to be provided, that the current IfcPropertySet is not included in its own List of HasProperties. |
EXPRESS Definition
Definition from IAI: The IfcPropertyTypeDef provides for the capability to:
As IFC Type Driven Properties do not require separate classes for each type, they can be defined at runtime. This is a significant advantage in providing flexibility and extensibility to application developers and end users of applications that support IFC.
The IfcPropertyTypeDef can be defined at two levels:
Type Definitions at the Specific Type level refer to the common Type Definition at the Generic Type level, where the common Properties are defined.
NOTE: This is an enhanced definition of the IFC Release 1.0 class IfcTypeDefinition.
ISSUE: See issues I-077, I-079, I-185, I-306GI-003 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ProjectId |
Assignment of a globally unique identifier that allows to ensure uniqueness in a global context. |
see type |
see type |
n/a |
|
|
OwnerHistory |
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. |
see type |
see type |
n/a |
|
|
TypeDefName |
Name of the Property Type Definition |
STRING |
see type |
see type |
n/a |
|
TypedClass |
Name of the Class for which this object defines a type |
STRING |
see type |
see type |
n/a |
Opt |
GenericType |
IFC defined generic type designation (e.g. 3 generic types of Space = Occupied, Technical, Circulation) |
STRING |
see type |
see type |
NIL |
Opt |
SpecificType |
IFC defined specific type designation to further decompose the parent, generic type. |
STRING |
see type |
see type |
NIL |
|
TypeDomainView |
Indication of the Domain View, in which the type is defined. |
Cross Domain |
Fac Mgmt |
Cross Domain |
|
|
SharedProperties |
Relationship to an IfcPropertySet which contains the set of Properties that are constant for all occurrences of this type |
SET [0:?] IfcSharedPropertySet |
see type |
see type |
n/a |
Opt |
GenericTypeReference |
Reference to a higher level type definition, currently used for a specific type to reference its generic type |
see type |
see type |
NIL |
|
INV |
ReferencedBySpecificType |
Notification of all lower level type definitions that exists (and expand) this type, used to note all specific types given for a generic type. |
Set [0:?] IfcPropertyTypeDef |
see type |
see type |
NIL |
INV |
OccurrenceSets |
Reference to the Occurrence Property Sets that are driven by this Type |
Set [0:?] IfcOccurrencePropertySet |
see type |
see type |
NIL |
Formal Propositions:
WR1 |
Either it is a Generic Type (GenericType exists) or a Specific Type (SpecificType exists). |
EXPRESS Definition
Definition from IAI: The IfcPropertyWithUnit defines an attribute class, for which the value -- unit -- name triple is given, where the name and the value are defined in the supertype IfcSimpleProperty.
NOTE: This is a new class within IFC Release 1.5, it replaces the several measure-with-unit classes, which have been defined in earlier releases.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
UnitComponent |
Unit of the property value. NOTE: this should only be used, if there is no predefined named data type within the IfcMeasureValue that associates the appropriate unit. |
see type |
see type |
n/a |
No formal or informal propositions defined at this level.
EXPRESS Definition
Definition from IAI: The IfcSharedPropertySet defines a set of type driven properties (and is therefore defined as part of the IFC standard) that are shared by multiple instances of a semantic object, i.e. each semantic object instance (having the same property values) shares by reference a single instance of the IfcSharedPropertySet with particular property values.
NOTE: This is a revised version of the IFC Release 1.0 class IfcAttributeObject.
ISSUE: See issue I-078 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
INV |
TypeDefined |
Reference to Type Definition, the reference is given to indicate the Property Type Definition that defines the Shared Type Defined Property. |
see type |
see type |
n/a |
Formal Propositions:
WR1 |
Product Shapes shall not be included in a Type Driven Property Set. |
EXPRESS Definition
Definition from IAI: The IfcSimpleProperty defines an attribute class, for which the value -- name pair is given. It shall be used for those simple properties, where the unit is already implied by the specific type of the IfcMeasureValue and the IfcUnitAssignment. For simple properties with measures that refer to more specific units, the IfcPropertyWithUnit shall be used.
NOTE: This is a revised version of the IFC Release 1.0 class IfcAttributeObject.
ISSUE: See issue I-080 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Rel Type |
Min |
Max |
Default |
|
Descriptor |
Name that uniquely defines the Property in case of type driven properties, in case of extended properties the name must be agreed upon among the parties that communicate the extension. |
STRING |
see type |
see type |
n/a |
|
ValueComponent |
Value of this property. NOTE: By virtue of the defined data type, that is selected from the SELECT IfcMeasureValue the appropriate unit can be found within the unit assignment at the IfcProject. |
see type |
see type |
n/a |
No formal or informal propositions defined at this level.
EXPRESS Definition
Definition from IAI: The IfcProductShape defines all shape relevant information about an IfcProduct. It allows for multiple geometric shape representations.
NOTE: This is a new class in IFC Release 1.5. The definition of this class was influenced by the idea behind the ISO 10303-41 entity product_definition_shape.
ISSUE: See issues I-041, I-044, I-047, I-048, GI-002, GI-003 for
changes made in IFC Release 1.5.
See issue I-330 for changes made in IFC Release 1.5.1.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ProjectId |
Assignment of a globally unique identifier that allows to ensure uniqueness in a global context. |
see type |
see type |
n/a |
|
|
ShapeRepresentations |
Contained list of shape representations. Each member defining a valid shape representation of a particular type (i.e. bounding box, attribute driven, explicit) within a particular representation context. |
List [1:?] IfcShapeRepresentation |
see type |
see type |
n/a |
OPT |
Descriptor |
User interpretable Descriptor for the Product Shape. |
STRING |
see type |
see type |
NIL |
INV |
HasShapeAspects |
Reference to the shape representation, explicitly indication aspects or components of the product shape. |
Set [0:?] IfcShapeAspect |
see type |
see type |
NIL |
No formal or informal propositions defined at this level.
Class IfcRepresentationContext
EXPRESS Definition
Definition from IAI: The IfcRepresentationContext defines the geometric and view type context that applies to several shape representations of semantic objects in IFC. It defines the view in which the shape representation is defined, the level of detailing for which the shape representation is valid and the numeric precision used to define the geometric representation items.
NOTE: New class in IFC Release 1.5, the definition of this class was influenced by the idea behind the ISO 10303-43 entity representation_context.
ISSUE: See issues I-049, I-051 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ProjectId |
Assignment of a globally unique identifier that allows to ensure uniqueness in a global context. |
see type |
see type |
n/a |
|
|
DetailType |
Indication of the level of detail to which the representation applies. |
Sketch |
Undefined |
Undefined |
|
|
ViewType |
Indication of the projection in which the representation is defined. |
Plan |
Undefined |
Undefined |
|
|
Precision |
Defines the numeric precision used for the coordinates within the geometric representation items |
INTEGER |
see type |
see type |
n/a |
INV |
RepresentationsInContext |
All shape representations that are defined in the same representation context. |
Set [1:?] IfcShapeRepresentation |
see type |
see type |
n/a |
No formal or informal propositions defined at this level.
EXPRESS Definition
Definition from IAI: The shape aspect is an identifiable element of the shape of a product. The IfcShapeAspect allows for grouping of shape representation items that represent aspects (or components) of the Product Shape. Thereby shape representations of components of the product shape representing a semantically defined Product can be explicitly addressed.
NOTE: New class in IFC Release 1.5.1. The definition of this class was influenced by the idea behind the ISO 10303-41 entity shape_aspect.
ISSUE: See issues I-330 for changes made in IFC Release 1.5.1.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ProjectId |
Assignment of a globally unique identifier that allows to ensure uniqueness in a global context. |
see type |
see type |
n/a |
|
|
ShapeRepresentations |
Contained list of shape representations. Each member defining a valid shape representation of a particular type (i.e. bounding box, attribute driven, explicit) within a particular representation context. |
List [1:?] IfcShapeRepresentation |
see type |
see type |
n/a |
|
Descriptor |
Tag to indicate the particular semantic of a component within the Product Shape, used to provide meaning. Example: use the tag "WindowFrame" to define which component of a window shape defines the frame. |
STRING |
see type |
see type |
n/a |
|
PartOfProductShape |
Reference to the product shape of which this class is an aspect. |
see type |
see type |
n/a |
No formal propositions defined at this level.
Informal Propositions:
IR1 |
The IfcShapeRepresentation, that defines representation items for the shape aspect shall only contain a subset of those representation items, which are defined for the IfcShapeRepresentation of the IfcProductShape to which the IfcShapeAspect belongs. |
EXPRESS Definition
Definition from IAI: The IfcShapeRepresentation defines the concept of a particular geometric Representation of a Product Component within a special Representation Context.
NOTE: New class in IFC Release 1.5. The definition of this class was influenced by the idea behind the ISO 10303-43 entity representation
ISSUE: See issues I-043, I-052, I-184, I-194 for changes made in IFC Release 1.5.
|
Attribute / Relation |
Definition |
Data or Rel Type |
Min |
Max |
Default |
|
Items |
List of Geometric Representation Items that are defined for this representation |
List[1:?] IfcGeometricRepresentationItem |
see type |
see type |
n/a |
|
ContextOfItems |
Definition of the representation context for which the Shape Representation is valid |
see type |
see type |
n/a |
|
|
RepresentationType |
Indication of the type of Shape Representation, i.e. either Bounding Box, Attribute Driven, or Explicit |
BoundingBox |
Arbitrary |
BoundingBox |
|
Opt |
UsageDescriptor |
Description of the usage for this Shape Representation, e.g. for site boundary, or site contour |
STRING |
see type |
see type |
NIL |
INV |
OfProductShape |
Reference to the product shape, for which it is the shape representation |
SET [0:1] IfcProductShape |
see type |
see type |
n/a |
INV |
OfShapeAspect |
Reference to the shape aspect, for which it is the shape representation |
SET [0:1] IfcShapeAspect |
see type |
see type |
NIL |
Formal Propositions:
WR1 |
Constrains the valid Items for representation according to the Shape Representation Type (IfcShapeRepTypeEnum) BoundingBox |
WR2 |
The IfcShapeRepresentation shall be either defined for a single product shape or for a single shape aspect. |