IFC 4.3.0.1 (IFC4X3_TC1)

6.5.3.2 IfcCostItem

6.5.3.2.1 Semantic definition

An IfcCostItem describes a cost or financial value together with descriptive information that describes its context in a form that enables it to be used within a cost schedule. An IfcCostItem can be used to represent the cost of goods and services, the execution of works by a process, lifecycle cost and more.

Each instance of IfcCostItem may have a name and a description. Depending on the use for which the cost is intended, these values should be asserted on the basis of agreement. For instance, the Name attribute could be used to provide a common value that enables distinct instances to be brought together in a nesting arrangement (see below) while the Description attribute may be used to provide text used for item description in a costing schedule.

An IfcCostItem can link one or many IfcCostValue's representing a unit cost, total cost, or a unit cost with one or many quantities used to generate the total cost. The quantities can be given as individual quantities, or those quantities are provided as element quantities by one or many building elements. The IfcCostValue.Category attribute indicates the category of cost, which may be used to present the value in a particular column. For nested cost items (having IfcRelNests relationship), IfcCostValue.Category is significant such that IfcCostValue.AppliedValue is calculated as the sum of all nested costs having the same IfcCostValue.Category or if set to an asterisk ('*'), then the sum of all nested costs of all cost types. An IfcCostValue may represent an original value or a value derived from formulas using IfcAppliedValueRelationship. For example, taxes may be calculated as a percentage of a subtotal.

6.5.3.2.2 Entity inheritance

6.5.3.2.3 Attributes

# Attribute Type Description
IfcRoot (4)
1 GlobalId IfcGloballyUniqueId

Assignment of a globally unique identifier within the entire software world.

2 OwnerHistory OPTIONAL IfcOwnerHistory

Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object,

3 Name OPTIONAL IfcLabel

Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.

4 Description OPTIONAL IfcText

Optional description, provided for exchanging informative comments.

IfcObjectDefinition (7)
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects

Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.

Nests SET [0:1] OF IfcRelNests FOR RelatedObjects

References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).

IsNestedBy SET [0:?] OF IfcRelNests FOR RelatingObject

References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).

HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions

References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.

IsDecomposedBy SET [0:?] OF IfcRelAggregates FOR RelatingObject

References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).

Decomposes SET [0:1] OF IfcRelAggregates FOR RelatedObjects

References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definitions can only be part of a single decomposition (to allow hierarchical strutures only).

HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects

Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification.

IfcObject (5)
5 ObjectType OPTIONAL IfcLabel

The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED or when the concrete entity instantiated does not have a PredefinedType attribute. The latter is the case in some exceptional leaf classes and when instantiating IfcBuiltElement directly.

IsDeclaredBy SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects

Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

Declares SET [0:?] OF IfcRelDefinesByObject FOR RelatingObject

Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

IsTypedBy SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects

Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type.

IsDefinedBy SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects

Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object.

IfcControl (2)
6 Identification OPTIONAL IfcIdentifier

An identifying designation given to a control It is the identifier at the occurrence level.

Controls SET [0:?] OF IfcRelAssignsToControl FOR RelatingControl

Reference to the relationship that associates the control to the object(s) being controlled.

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IfcCostItem (3)
7 PredefinedType OPTIONAL IfcCostItemTypeEnum

Predefined generic type for a cost item that is specified in an enumeration. There may be a property set given specifically for the predefined types.

8 CostValues OPTIONAL LIST [1:?] OF IfcCostValue

Component costs for which the total cost for the cost item is calculated, and then multiplied by the total CostQuantities if provided.

If CostQuantities is provided then values indicate unit costs, otherwise values indicate total costs.

For calculation purposes, the cost values may be directly added unless they have qualifications. Cost values with qualifications (e.g. IfcCostValue.ApplicableDate, IfcCostValue.FixedUntilDate) should be excluded from such calculation if they do not apply.

9 CostQuantities OPTIONAL LIST [1:?] OF IfcPhysicalQuantity

Component quantities of the same type for which the total quantity for the cost item is calculated as the sum.

Table 6.5.3.2.C

6.5.3.2.4 Concept usage

Concept Usage Description
IfcRoot (2)
Revision Control General

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

Software Identity General

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

IfcObjectDefinition (9)
Aggregation General

No description available.

Approval Association General

No description available.

Classification Association General

Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.

Constraint Association General

No description available.

Document Association General

No description available.

Library Association General

No description available.

Material Association General

No description available.

Material Single General

No description available.

Nesting General

No description available.

IfcObject (5)
Assignment to Group General

No description available.

Object Predefined Type General

No description available.

Object Typing General

Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject.

This concept can be applied to the following resources:

Object User Identity General

An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as ifcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.

Property Sets with Override General

Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case, that the same property (within the same property set, is defined both, in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.

IfcControl (1)
Control Assignment General

Controls have assignments from products, processes, or other objects by using the relationship object IfcRelAssignsToControl.

This concept can be applied to the following resources:

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IfcCostItem (3)
Classification Association General

Instances of IfcCostItem are used for cost estimates, budgets, and other forms, where a variety of identification codes are used extensively to identify the meaning of the cost. Examples include project phase codes, CSI codes, takeoff sequence numbers, and cost accounts. The model allows for all classes that are ultimately subtypes of IfcObject to inherit the ability to have one or more instances of IfcClassificationReference to be assigned. Where identification codes are required, the generic IfcRelAssociatesClassification facility should be used.

Control Assignment General

An IfcCostItem can be calculated based on quantities from objects through its relationship to IfcRelAssignsToControl.

For quantity-based costing, IfcElement, IfcTask, or IfcResource occurrence subtypes may be used. Multiple elements may be assigned of the same or different types, using IfcPhysicalQuantity entities defined at each object. Each IfcPhysicalQuantity type must be identical (for example, all values are IfcAreaQuantity) such that they can be added together.

For rate-based costing (specifically for IfcCostScheduleTypeEnum.SCHEDULEOFRATES), a single IfcTypeProduct, IfcTypeProcess, or IfcTypeResource subtype may be used to reflect rates for occurrences of such types. This enables the possibility to generate a quantity-based cost schedule for occurrences based on types with rate-based cost schedules.

IfcRelAssignsToControl is also used in the opposite direction to link the root IfcCostItem to an IfcCostSchedule where RelatingControl is the IfcCostSchedule.

Figure 6.5.3.2.A illustrates cost item assignment derived from building elements. The IfcRelAssignsToControl relationship indicates building elements for which quantities are derived. Not shown, costs may also be derived from building elements by traversing assignment relationships from the assigned IfcProduct to IfcProcess to IfcResource, where all costs ultimately originate at resources. It is also possible for cost items to have assignments from processes or resources directly.

cost item
Figure 6.5.3.2.A — Cost assignment

This concept can be applied to the following resources:

  • IfcProduct - For quantity-based costs based on product occurrences, spatial structures, or other physical artifacts.
  • IfcProcess - For quantity-based costs based on tasks, procedures, or events.
  • IfcResource - For quantity-based costs based on resource allocations.
  • IfcTypeProduct - For cost rates based on product models.
  • IfcTypeProcess - For cost rates based on process models of historical or projected duration.
  • IfcTypeResource - For cost rates based on resource models of historical or projected productivity.
Object Nesting General

An IfcCostItem can nest other instances of IfcCostItem through its relationships to IfcRelNests. This can be used to enable the development of complex groups of costs as may be found in cost schedules through to pages, sections and complete cost schedules.

There is always a summary cost item as the root item of the tree representing the cost item nesting. Subsequent instances of IfcCostItem are assigned to the summary cost item using IfcRelNests. The summary cost item itself is assigned to IfcCostSchedule through the IfcRelAssignsToControl relationship.

Figure 6.5.3.2.B illustrates a cost item composition used for a cost schedule. Each line item has a quantity and separate unit costs where IfcCostValue.Category indicates the category of cost. The summary item has a hierarchy of costs calculated according to IfcAppliedValueRelationship.ArithmeticOperator, where IfcCostValue.Category identifies the category to be totalled. The Tax component has IfcCostValue.Category set to 'Material' which indicates it is the sum of all nested values of the 'Material' category ($3 x 3000 + $118 x 100 = $20800). The Subtotal component has IfcCostValue.Category set to an asterisk ('*') which indicates it is the sum of all nested values of all categories.

cost item
Figure 6.5.3.2.B — Cost composition

This concept can be applied to the following resources:

Table 6.5.3.2.D

6.5.3.2.5 Formal representation

ENTITY IfcCostItem
 SUBTYPE OF (IfcControl);
	PredefinedType : OPTIONAL IfcCostItemTypeEnum;
	CostValues : OPTIONAL LIST [1:?] OF IfcCostValue;
	CostQuantities : OPTIONAL LIST [1:?] OF IfcPhysicalQuantity;
END_ENTITY;

6.5.3.2.6 References

6.5.3.2.7 Changelog

6.5.3.2.7.1 IFC4

  • attribute, CostQuantities
  • attribute, CostValues
  • attribute, PredefinedType