IfcLagTime

BACnet MVD

#### IfcLagTime

Natural language names

| Zeitlicher Abstand
| Lag Time
| Décalage entre processus

Change log

Item | SPF | XML | Change | Description
--- | --- | --- | --- | ---
IFC2x3 to IFC4
IfcLagTime |  |  | ADDED |

##### Semantic definitions at the entity

Entity definition

IfcLagTime describes the time parameters that may exist within a sequence relationship between two processes.

An IfcLagTime provides information about the time lag that exists between the predecessor and successor process in a sequence. The assertion of the time lag is optional for a sequence but for work schedules that specifically deal with processes occurring at particular times, it should be asserted.

A lag time has a duration type. This allows the identification of whether elapsed time or work time is being measured (where work time is the estimate of the time required to complete the process and elapsed time being the amount of time actually allocated to the process)

The form of measurement of the duration can be captured. Allowed values for this are MEASURED, PREDICTED or SIMULATED. The selection of this value depends on the use of the schedule. A NOTDEFINED value is also allowed.

The value of the time lag may be selected as being either a percentage ratio or an actual time measure. If selected as a ratio, the percentage should apply to the duration of the predecessor process (relating process) such that e.g. a value of 0.5 (50%) would indicate that the successor task should start when the predecessor task is 50% complete (if a START-START sequence type is used) or should wait for 50% of the duration of the predecessor process to have elapsed after the finish of the predecessor process in case of a FINISH-START sequence type.

The time unit for the task duration may also be set and this may be set to any allowed unit of time measure.

> HISTORY New entity in IFC4.

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
4 | LagValue | IfcTimeOrRatioSelect |  | Value of the time lag selected as being either a ratio or a time measure. |  | X
5 | DurationType | IfcTaskDurationEnum |  | The allowed types of task duration that specify the lag time measurement (work time or elapsed time). |  | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcSchedulingTime
1 | Name | IfcLabel | ? | Optional name for the time definition. |  | X
2 | DataOrigin | IfcDataOriginEnum | ? | Specifies the origin of the scheduling time entity. It currently differentiates between predicted, simulated, measured, and user defined values. |  | X
3 | UserDefinedDataOrigin | IfcLabel | ? | Value of the data origin if DataOrigin attribute is USERDEFINED. |  | X
IfcLagTime
4 | LagValue | IfcTimeOrRatioSelect |  | Value of the time lag selected as being either a ratio or a time measure. |  | X
5 | DurationType | IfcTaskDurationEnum |  | The allowed types of task duration that specify the lag time measurement (work time or elapsed time). |  | X

##### Formal representations

XML Specification
`<xs:element name="IfcLagTime" type="ifc:IfcLagTime" substitutionGroup="ifc:IfcSchedulingTime" nillable="true"/>
<xs:complexType name="IfcLagTime">
<xs:complexContent>
<xs:extension base="ifc:IfcSchedulingTime">
<xs:sequence>
<xs:element name="LagValue">
<xs:complexType>
<xs:group ref="ifc:IfcTimeOrRatioSelect"/>
</xs:complexType>
</xs:element>
</xs:sequence>
<xs:attribute name="DurationType" type="ifc:IfcTaskDurationEnum" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcLagTime
SUBTYPE OF (IfcSchedulingTime);
LagValue : IfcTimeOrRatioSelect;
DurationType : IfcTaskDurationEnum;
END_ENTITY;

EXPRESS-G diagram

`

References: IfcRelSequence

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