IfcTask是在建设项目中执行的可识别的工作单元。
任务通常用于描述产品的构造或安装活动，但不限于这些类型。例如，它可以用来描述设计过程、移动操作以及其他与设计、施工和操作相关的活动。
任务消耗的资源量是通过定义资源的IfcElementQuantity来处理的，而不是在IfcTask实例中
属性使用定义:
每出现一个IfcTask都会给出一个表示其内容的名称（IfcRoot.name）。可以提供任务的文本描述，这可以通过叙述性的长描述（IfcProcess.long description）进一步阐述。可以为执行任务时使用的工作方法声明工作方法。任务被标识为是否是里程碑任务。里程碑任务由标记is milestone定义。没有持续时间。还可以为每个任务设置状态和优先级。
时间和持续时间使用定义:
与以前的IFC版本相比，基本任务时间信息（计划开始时间、计划完成时间、持续时间）现在通过task time属性直接附加到IFC task。常规任务通过IfcTaskTime定义。周期性任务是通过ifctasktimerencial定义的。如果常规任务派生自定期任务，则应通过IfcRelNests关系将两个任务链接在一起，其中IfcRelNests.IsNestedBy指向定期任务，IfcRelNests.Nests指向从定期任务派生的所有常规任务。
其他活动的代表:
IfcTask的使用定义也被概括为表示其他活动，包括在以前的IFC版本中由自己的实体定义的活动。这包括
■命令操作
■移动操作
IfcTask表示服务台执行的一个命令，该服务台充当设施用户与满足其需求的功能需求之间的组织接口角色。IfcTask实体表示的实际任务是将请求转换为订单并启动将使订单得以完成的操作。ifcprojector或其子类型之一（包括维护工单）与使用IfcRelAssignsToControl的IfcTask相关。
IfcTask还可用于描述将人员、组织内的组或完整组织及其相关家具和设备从一个地方移动到另一个地方的活动。因此，它取代了先前的国际金融公司实体IfcMove。功能在IfcTask中表示如下：
①移除：演员及其相关设备搬离的地方。
使用IfcRelAssignsToProcess，relationprocess指向任务，RelatedObjects保存要从中移动的位置。
②移动：演员及其相关设备移动到的位置。
使用IfcRelAssignsToProduct，其中RelatedObjects指向任务，RelatingProduct指向要移动到的位置。
③剩余工作清单：需要注意的动作的要点清单。
使用LongDescription或其他标识子任务，通过IfcRelNests单独跟踪尾项列表项。
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 |