IFC 4.3.x development

5.3.3.6 IfcTask

Change log

IFC4

additions attributes IsMilestone
additions attributes PredefinedType
additions where_rules CorrectPredefinedType
additions where_rules HasName
deletions attributes TaskId
deletions where_rules WR1
deletions where_rules WR2
deletions where_rules WR3
modificationsattributes IsMilestone definition Changed from boolean to IfcInteger
modificationsattributes IsMilestone is_optionalChanged from False to True
modificationsattributes IsMilestone name Changed from IsMilestone to Priority
modificationsattributes Priority definition Changed from integer to IfcTaskTime
modificationsattributes Priority name Changed from Priority to TaskTime

5.3.3.6.1 Semantic definitions at the entity

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.

5.3.3.6.1 Attributes

# Attribute Type Description
IfcRoot
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,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
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
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).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
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).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
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.

> IFC4 CHANGE  The inverse attribute datatype has been added.
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).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
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).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociationsSET [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 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.
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.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
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.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
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.

> 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.
IsDefinedBy SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjectsSet 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.
IfcProcess
6 Identification OPTIONAL IfcIdentifier An identifying designation given to a process or activity.

It is the identifier at the occurrence level.



> IFC4 CHANGE Attribute promoted from subtypes.
7 LongDescriptionOPTIONAL IfcText An extended description or narrative that may be provided.

> IFC4 CHANGE  New attribute.
IsPredecessorToSET [0:?] OF IfcRelSequence FOR RelatingProcess 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.
IsSuccessorFromSET [0:?] OF IfcRelSequence FOR RelatedProcess 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.
OperatesOn SET [0:?] OF IfcRelAssignsToProcess FOR RelatingProcess Set of relationships to other objects, e.g. products, processes, controls, resources or actors, that are operated on by the process.
IfcTask
8 Status OPTIONAL IfcLabel 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'.
9 WorkMethod OPTIONAL IfcLabel 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
10 IsMilestone IfcBoolean 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.
11 Priority OPTIONAL IfcInteger A value that indicates the relative priority of the task (in

comparison to the priorities of other tasks).
12 TaskTime OPTIONAL IfcTaskTime Time related information for the task.



> IFC4 CHANGE Attribute added
13 PredefinedType OPTIONAL IfcTaskTypeEnum Identifies the predefined types of a task from which

the type required may be set.



> IFC4 CHANGE Attribute added

5.3.3.6.2 Entity inheritance

dot_inheritance IfcTask IfcTask IfcProcess IfcProcess IfcTask->IfcProcess IfcEvent IfcEvent IfcEvent->IfcProcess IfcObject IfcObject IfcProcess->IfcObject IfcProcedure IfcProcedure IfcProcedure->IfcProcess IfcObject_children 5 more... IfcObject_children->IfcObject IfcObjectDefinition IfcObjectDefinition IfcObject->IfcObjectDefinition IfcContext IfcContext IfcContext->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

5.3.3.6.3 Definitions applying to General Usage

5.3.3.6.3.1 Classification

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.

5.3.3.6.3.2 Classification Association

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.

5.3.3.6.3.3 Constraint

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.

5.3.3.6.3.4 Control Assignment

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.

5.3.3.6.3.5 Identity

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

5.3.3.6.3.6 Nesting

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 139, 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.

task example

Figure 139 — Task visualization

A task may nest other tasks as sub-items; the nesting relationship is modeled by IfcRelNests as shown in Figure 140. 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.

task instantiation diagram

Figure 140 — Task nesting relationships

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

5.3.3.6.3.7 Object Predefined Type

5.3.3.6.3.8 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.
RelatingType
'IfcTaskType'

5.3.3.6.3.9 Object User Identity

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.

5.3.3.6.3.10 Process Assignment

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.

5.3.3.6.3.11 Product Assignment

5.3.3.6.3.12 Property Sets

PsetName PredefinedType
'Pset_PackingInstructions''MOVE'

5.3.3.6.3.13 Property Sets for Objects

PsetName
'Pset_Risk'

5.3.3.6.3.14 Property Sets with Override

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.

5.3.3.6.3.15 Revision Control

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

5.3.3.6.3.16 Sequential Connectivity

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.

5.3.3.6.4 Formal representations

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;