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 to IFC4 ADD1
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	B
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	-		This attribute is out of scope for this model view definition and shall not be set.
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	B
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).
	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.
	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	-		This attribute is out of scope for this model view definition and shall not be set.
	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
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	-		This attribute is out of scope for this model view definition and shall not be set.
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 Bridge View

Instance diagram

The sequencing of construction may be specified for various reasons: to maintain a level of service of existing roadways during construction; to coordinate timing of a project with other related projects; and to define expected structural loads during construction. Most commonly, the sequencing of bridge girders is indicated for structural design purposes. There may also be use cases for exporting to other applications supporting construction scheduling or erection plans and procedures.

Tasks are used to indicate construction phases and may be assigned to building elements to indicate subsets of the project to be constructed or otherwise impacted at particular sequences.

Tasks may have structural analysis models assigned to indicate structural loads and results at particular phases.

Each phase of a project may be represented by IfcTask. The IfcTask entity defines anything occurring in time over a time span and may correspond to a high-level summary task such as a construction stage, very-low level tasks such as placing a specific beam, or anything in between and a combination of all. Tasks may be nested into subtasks for drilling into detail using the IfcRelNests relationship. An IfcTask instance may be assigned to elements affected by the task using IfcRelAssignsToProduct. The meaning of a task may be further defined by IfcTask.PredefinedType, e.g. CONSTRUCT means to fabricate the element, INSTALL means to place the element, DEMOLISH means to destroy the element, REMOVE means to uninstall the element. In addition to specific meaning for construction, applications that support 4D animation of construction schedules may also make use of such designations for presentation purposes.

Figure 1 — Bridge phase modell

Concept usage

Object Nesting

The Object Nesting concept applies to this entity as shown in Table 6.

Type	Description
IfcTask	Tasks may be nested into subtasks.

Table 6 — IfcTask Object Nesting

Exchange
Import		O
Export		O

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.

Exchange
Import		O
Export		O

Task Attributes

The Task Attributes concept applies to this entity.

Exchange
Import		O
Export		O

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Bridge View
	User Identity	Bridge View
	Object Ownership	Bridge View
IfcObject
	Property Sets for Objects	Bridge View
IfcTask
	Object Nesting	Bridge View
	Sequential Connectivity	Bridge View
	Task Attributes	Bridge View

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="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 IfcStrippedOptional;

  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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