IfcTask

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcTask
OwnerHistory			MODIFIED	Instantiation changed to OPTIONAL.
Identification		X	MODIFIED	Name changed from TaskId to Identification. Instantiation changed to OPTIONAL.
LongDescription			MODIFIED	Name changed from Status to LongDescription. Type changed from IfcLabel to IfcText.
Status		X	MODIFIED	Name changed from WorkMethod to Status.
WorkMethod	X	X	MODIFIED	Name changed from IsMilestone to WorkMethod. Type changed from BOOLEAN to IfcLabel. Instantiation changed to OPTIONAL.
IsMilestone	X	X	MODIFIED	Name changed from Priority to IsMilestone. Type changed from INTEGER to BOOLEAN. Instantiation changed from OPTIONAL.
Priority			ADDED
TaskTime			ADDED
PredefinedType			ADDED
IFC4 Addendum 1
IfcTask
IsMilestone			MODIFIED	Type changed from BOOLEAN to IfcBoolean.
Priority			MODIFIED	Type changed from INTEGER to IfcInteger.

Semantic definitions at the entity

Entity definition

An IfcTask is an identifiable unit of work to be carried out in a construction project.

A task is typically used to describe an activity for the construction or installation of products, but is not limited to these types. For example it might be used to describe design processes, move operations and other design, construction and operation related activities as well.

Quantities of resources consumed by the task are dealt with by defining the IfcElementQuantity for the resource and not at the instance of IfcTask.

HISTORY New entity in IFC1.0. Renamed from IfcWorkTask in IFC2x.

IFC4 CHANGE Attributes TaskTime and PredefinedType added. IfcMove and IfcOrderRequest has been removed in IFC4 and are now represented by IfcTask. IfcRelAssignsTasks relationship has been removed as well.

Attribute use definition

Each occurrence of IfcTask is given a name that is indicative of its content (IfcRoot.Name). A textual description of the task may be provided and this may be further elaborated by a narrative long description (IfcProcess.LongDescription). A work method may be declared for the method of work used in carrying out a task. A task is identified as being either a milestone task or not. A milestone task is defined by the marker IsMilestone. and has no duration. A status and priority for each task may also be set.

Time and duration use definition

Compared to previous IFC releases, basic task time information (scheduled start time, scheduled finish time, duration) is now directly attached to IfcTask through the TaskTime attribute. Regular tasks are defined through IfcTaskTime. Recurring tasks are defined through IfcTaskTimeRecurring. In case a regular task is derived from a recurring task both tasks should be linked together through a IfcRelNests relationship, where IfcRelNests.IsNestedBy points to the recurring task and IfcRelNests.Nests points to all regular tasks that have been derived from the recurring task.

Representation of other activities

The use definitions for IfcTask have been generalised to represent other activities as well, including activities that had been defined by own entities in previous IFC releases. This includes

Order actions
Move operations

IfcTask represents an order that might be carried out by a Helpdesk acting the role of interface for the organization between the facility user and the functional requirement of fulfilling their needs. The actual task represented by the IfcTask entity is turning a request into an order and initiating the action that will enable the order to be completed. The IfcProjectOrder or one of its subtypes including maintenance work order, is related to the IfcTask using IfcRelAssignsToControl.

IfcTask can also be used to describe an activity that moves people, groups within an organization or complete organizations together with their associated furniture and equipment from one place to another. It thus replaces the previous IFC entity IfcMove. The functionality is represented in IfcTask as follows:

Move from: The place from which actors and their associated equipment are moving.
Use IfcRelAssignsToProcess where RelatingProcess points to the task and RelatedObjects holds the location(s) from which to move.
Move to: The place to which actors and their associated equipment are moving.
Use IfcRelAssignsToProduct where RelatedObjects points to the task(s) and RelatingProduct points to the location to which to move.
Punch list: A list of points concerning a move that require attention.
Use LongDescription or else identify sub-tasks to track punch list items individually via IfcRelNests.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
8	Status	IfcLabel	[0:1]	Current status of the task. NOTE Particular values for status are not specified, these should be determined and agreed by local usage. Examples of possible status values include 'Not Yet Started', 'Started', 'Completed'.	X
9	WorkMethod	IfcLabel	[0:1]	The method of work used in carrying out a task. NOTE This attribute should not be used if the work method is specified for the IfcTaskType	X
10	IsMilestone	IfcBoolean	[1:1]	Identifies whether a task is a milestone task (=TRUE) or not (= FALSE). NOTE In small project planning applications, a milestone task may be understood to be a task having no duration. As such, it represents a singular point in time.	X
11	Priority	IfcInteger	[0:1]	A value that indicates the relative priority of the task (in comparison to the priorities of other tasks).	X
12	TaskTime	IfcTaskTime	[0:1]	Time related information for the task.	X
13	PredefinedType	IfcTaskTypeEnum	[0:1]	Identifies the predefined types of a task from which the type required may be set.	X

Formal Propositions

Rule	Description
HasName	The Name attribute should be inserted to describe the task name.
CorrectPredefinedType	The attribute ObjectType must be asserted when the value of PredefinedType is set to USERDEFINED.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	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.	X
3	Name	IfcLabel	[0:1]	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	[0:1]	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).	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).	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.	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).	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).	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	[0:1]	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.	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.	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.	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.	X
IfcProcess
6	Identification	IfcIdentifier	[0:1]	An identifying designation given to a process or activity. It is the identifier at the occurrence level.	X
7	LongDescription	IfcText	[0:1]	An extended description or narrative that may be provided.	X
	IsPredecessorTo	IfcRelSequence @RelatingProcess	S[0:?]	Dependency between two activities, it refers to the subsequent activity for which this activity is the predecessor. The link between two activities can include a link type and a lag time.	X
	IsSuccessorFrom	IfcRelSequence @RelatedProcess	S[0:?]	Dependency between two activities, it refers to the previous activity for which this activity is the successor. The link between two activities can include a link type and a lag time.	X
	OperatesOn	IfcRelAssignsToProcess @RelatingProcess	S[0:?]	Set of relationships to other objects, e.g. products, processes, controls, resources or actors, that are operated on by the process.	X
IfcTask
8	Status	IfcLabel	[0:1]	Current status of the task. NOTE Particular values for status are not specified, these should be determined and agreed by local usage. Examples of possible status values include 'Not Yet Started', 'Started', 'Completed'.	X
9	WorkMethod	IfcLabel	[0:1]	The method of work used in carrying out a task. NOTE This attribute should not be used if the work method is specified for the IfcTaskType	X
10	IsMilestone	IfcBoolean	[1:1]	Identifies whether a task is a milestone task (=TRUE) or not (= FALSE). NOTE In small project planning applications, a milestone task may be understood to be a task having no duration. As such, it represents a singular point in time.	X
11	Priority	IfcInteger	[0:1]	A value that indicates the relative priority of the task (in comparison to the priorities of other tasks).	X
12	TaskTime	IfcTaskTime	[0:1]	Time related information for the task.	X
13	PredefinedType	IfcTaskTypeEnum	[0:1]	Identifies the predefined types of a task from which the type required may be set.	X

Definitions applying to Common Use Definitions

Instance diagram

Concept usage

Object Typing

The Object Typing concept applies to this entity as shown in Table 14.

Type
IfcTaskType

Table 14 — IfcTask Object Typing

The IfcTask defines the anticipated or actual occurrence of any task; common information about task types is handled by IfcTaskType.

EXAMPLE It includes fixed duration, fixed unit or fixed work. An IfcTask can be aggregated to a task type in order to specify a task sequence or any time related information, e.g. the duration of a task. Please see the documentation of IfcTaskType for further information.

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 15.

PredefinedType

Name

Properties

MOVE

Pset_PackingInstructions

Pset_Risk

Single Value

Name	Value
NatureOfRisk	IfcLabel
SubNatureOfRisk1	IfcLabel
SubNatureOfRisk2	IfcLabel
RiskCause	IfcText
AffectsSurroundings	IfcBoolean

Enumerated Value

Name	Value	Value
RiskType	IfcLabel	IfcLabel
AssessmentOfRisk	IfcLabel	IfcLabel
RiskConsequence	IfcLabel	IfcLabel
RiskRating	IfcLabel	IfcLabel
RiskOwner	IfcLabel	IfcLabel

Table 15 — IfcTask Property Sets for Objects

Object Nesting

The Object Nesting concept applies to this entity.

IfcTask may be contained within an IfcTask using the IfcRelNests relationship. An IfcTask may in turn nest other IfcTask, IfcProcedure or IfcEvent entities. Such nesting indicates decomposed level of detail. From IFC4 onwards it is required to have a summary task (root of all tasks), which is used to define a link to the work plan or work schedule. All subtasks of the summary tasks are then implicitly linked to this work plan or work schedule. Please note that the summary task is used for data organization and not meant to store typical task information as defined by the user. It is therefore recommended that the summary task is hidden from the user to avoid confusion. Please also note that IfcRelNests is used to show the dependency between regular tasks and recurring task definitions (please see the section about time and duration use definitions).

As shown in Figure 130, the installation of a number of items of equipment within a particular space may be the subject of a single task which is identified as 'fix equipment in space 123'. IfcTask represents the occurrence of a work performance of a type of process in a construction plan.

Figure 130 — Task visualization

A task may nest other tasks as sub-items; the nesting relationship is modeled by IfcRelNests as shown in Figure 131. For example, the construction of a stud wall may be designated as a nesting task named 'install wall #1' including other tasks such as 'install dry wall', 'install studs', 'wall taping', and 'erect wall' as sub-processes. A value that indicates the relative tree view position of the task (in comparison to the tree view position of other tasks and the task hierarchy defined by IfcRelNests).

The task order information that is used for viewing purposes is derived from the order defined by the IfcRelNests relationship and thus is independent of the logical task order defined through IfcRelSequence. The hierarchy and order defined through IfcRelNests enables to order the tasks in a tree view or list view structure.

Figure 131 — Task nesting relationships

A top-level task is declared within the IfcProject using the IfcRelDeclares relationship.

Sequential Connectivity

The Sequential Connectivity concept applies to this entity.

The relationship IfcRelSequence is used to indicate control flow. An IfcTask as a successor to an IfcTask indicates logical sequence how these tasks should be performed. IfcTask's can be triggered or can trigger IfcEvent's, which is also defined through the relationship IfcRelSequence.

Control Assignment

The Control Assignment concept applies to this entity.

Occurrences of IfcTask may be assigned to an IfcWorkControl (either a work plan or a work schedule) through IfcRelAssignsToControl. Please note that the IfcRelAssignsTasks relationship class has been removed in IFC4 and is no longer available.

Process Assignment

The Process Assignment concept applies to this entity.

It is suggested to use the 'summary task' (root element of the task hierarchy that is required for task management purposes) to assign all subtask to a work plan or work schedule. Resources used by tasks are assigned by IfcRelAssignsToProcess.

Product Assignment

The Product Assignment concept applies to this entity.

Classification Association

The Classification Association concept applies to this entity.

An IfcTask may be assigned a Work Breakdown Structure (WBS) code. A WBS code is dealt with as a classification of task and is associated to a task occurrence using the IfcRelAssociatesClassification relationship class. As well as being to designate the code, the classification structure also enables the source of the work breakdown structure classification to be identified.

Constraint Association

The Constraint Association concept applies to this entity as shown in Table 16.

DataValue	Attribute1	Description
		Indicate fixed duration of task with ConstraintGrade=HARD and Benchmark=EQUALTO such that changes to an assigned IfcConstructionResource.ResourceTime.ScheduleWork should impact IfcConstructionResource.ResourceTime.ScheduleUsage, and vice-versa.

Table 16 — IfcTask Constraint Association

Constraints may be applied to a task to indicate fixed task duration, fixed start or fixed finish, where IfcMetric.ReferencePath is set to the corresponding attribute on the IfcTaskTime entity.

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Common Use Definitions
	Revision Control	Common Use Definitions
IfcObject
	Object Occurrence Predefined Type	Common Use Definitions
IfcProcess
IfcTask
	Object Typing	Common Use Definitions
	Property Sets for Objects	Common Use Definitions
	Object Nesting	Common Use Definitions
	Sequential Connectivity	Common Use Definitions
	Control Assignment	Common Use Definitions
	Process Assignment	Common Use Definitions
	Product Assignment	Common Use Definitions
	Classification Association	Common Use Definitions
	Constraint Association	Common Use Definitions

Formal representations

XSD Specification

 <xs:element name="IfcTask" type="ifc:IfcTask" substitutionGroup="ifc:IfcProcess" nillable="true"/>

 <xs:complexType name="IfcTask">

  <xs:complexContent>

   <xs:extension base="ifc:IfcProcess">

    <xs:sequence>

     <xs:element name="TaskTime" type="ifc:IfcTaskTime" nillable="true" minOccurs="0"/>

    </xs:sequence>

    <xs:attribute name="Status" type="ifc:IfcLabel" use="optional"/>

    <xs:attribute name="WorkMethod" type="ifc:IfcLabel" use="optional"/>

    <xs:attribute name="IsMilestone" type="ifc:IfcBoolean" use="optional"/>

    <xs:attribute name="Priority" type="ifc:IfcInteger" use="optional"/>

    <xs:attribute name="PredefinedType" type="ifc:IfcTaskTypeEnum" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcTask

 SUBTYPE OF (IfcProcess);

  Status : OPTIONAL IfcLabel;

  WorkMethod : OPTIONAL IfcLabel;

  IsMilestone : IfcBoolean;

  Priority : OPTIONAL IfcInteger;

  TaskTime : OPTIONAL IfcTaskTime;

  PredefinedType : OPTIONAL IfcTaskTypeEnum;

 WHERE

  HasName : EXISTS(SELF\IfcRoot.Name);
  CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcTaskTypeEnum.USERDEFINED) OR ((PredefinedType = IfcTaskTypeEnum.USERDEFINED) AND EXISTS(SELF\IfcObject.ObjectType));
END_ENTITY;

 EXPRESS-G diagram

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