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  Specification for IfcProcessExtension  

EXPRESS Definition

EXPRESS-G Diagram

IDL Definition

Schema Semantic Definition

The IfcProcessExtension model allows for the capture of information concerning the work required in order to create a product. Work is identified either as individual work tasks or as nests of work tasks. Tasks may be aggregated to gather into other work tasks as work nests and provision is allowed for a single task to participate in more than one work task.

A work task can be used to describe a process for the construction or installation of more than one product object and is given a name that is indicative of its content. EXAMPLE: The installation of a number of items of equipment within a particular space may be the subject of a single work task which is identified as 'fix equipment in space 123'.

EXAMPLE: The initial installation of all electrical equipment on a particular storey of a building may be designated as a work task named 'first fix electrical 3rd floor'. Work tasks are also given identifiers which enable them to be referenced against a construction plan (note that these identifiers are not the same as the unique identifiers inherited from IfcObject).

A work schedule identifies the time that a work task may be scheduled to take to complete and the model enables the capture of typical date and duration information that may be available from or for planning software.

Type IfcTaskStatusEnum

EXPRESS Definition

Type Semantic Definition

A list of possible status values that can be assigned to a work task. Allowed values are:-

Enumeration:

Completed
Started
NotYetStarted

Class IfcRelNestsProcesses

EXPRESS Definition

Class Semantic Definition

A subtype of IfcRelNests from the Kernel schema. This entity provides a nesting mechanism for IfcWorkTask so that any instance of IfcWorkTask and its subtypes are able to contain other instances of IfcWorkTask.

NOTE: This is a new class in Release IFC 1.5.1.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
OPT	NestingPurpose	A description of the purposes of the nesting.	STRING	see type	see type	empty
OPT	NestingCriteria	A description of the criteria of how the nested 'sub-processes' are selected.	STRING	see type	see type	empty

Formal Propositions:

WR31	Nesting object must be of type IfcWorkTask.
WR32	Nesting objects must be of type IfcWorkTask.

Interface Definitions

• I_RelNestsProcesses

Type Definitions

This class is not typed -- there is no type definition.

Class IfcWorkSchedule

EXPRESS Definition

Class Semantic Definition

The allocation of date and duration to a work task or work group. The work schedule is selected for either a work task or for a work group. A work group is represented by a work task which nests other work tasks.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
OPT	ActualStart	The date on which a work task is actually started.  NOTE - The scheduled start date must be greater than or equal to the earliest start date.  No constraint is applied to the actual start date with respect to the scheduled start date since a work task may be started than had originally been scheduled if circumstances allow.	IfcDateTimeSelect	see type	see type	NIL
OPT	EarliestStart	The earliest date on which a work task can be started.	IfcDateTimeSelect	see type	see type	NIL
OPT	LatestStart	The latest date on which a work task can be started.	IfcDateTimeSelect	see type	see type	NIL
OPT	ActualFinish	The date on which a work task is actually finished.	IfcDateTimeSelect	see type	see type	NIL
OPT	EarliestFinish	The earliest date on which a work task can be finished.	IfcDateTimeSelect	see type	see type	NIL
OPT	LatestFinish	The latest date on which a work task can be finished.	IfcDateTimeSelect	see type	see type	NIL
OPT	StatusTime	The date or time at which the status of the tasks within the programme is analysed.	IfcDateTimeSelect	see type	see type	NIL
OPT	ScheduledStart	The date on which a work task is scheduled to be started.  NOTE - The scheduled start date must be greater than or equal to the earliest start date.	IfcDateTimeSelect	see type	see type	NIL
OPT	ScheduledFinish	The date on which a work task is scheduled to be finished  NOTE - The scheduled finish date must be greater than or equal to the earliest finish date.	IfcDateTimeSelect	see type	see type	NIL
OPT	ScheduledDuration	The amount of time which is scheduled for completion of a work task.  NOTE - Scheduled Duration may be calculated as the time from scheduled start date to scheduled finish date.	IfcTimeDurationMeasure	see type	see type	NIL
OPT	RemainingTime	The amount of time remaining to complete a work task   NOTE - The time remaining in which to complete a work task may be determined both for tasks which have not yet started and those which have. Remaining time for a task not yet started has the same value as the scheduled duration. For a work task already started, remaining time is calculated as the difference between the scheduled finish and the point of analysis.	IfcTimeDurationMeasure	see type	see type	NIL
OPT	FreeFloat	The amount of time during which the start or finish of a work task may be varied without any effect on the overall programme of work.	IfcTimeDurationMeasure	see type	see type	NIL
OPT	TotalFloat	The difference between the duration available to carry out a work task and the scheduled duration of the task.   NOTE - Total Float time may be calculated as being the difference between the scheduled duration of a work task and the available duration from earliest start to latest finish. Float time may be either positive, zero or negative. Where it is zero or negative, the task becomes critical.	IfcTimeDurationMeasure	see type	see type	NIL
OPT	TaskStatus	Current status of the task.  NOTE - A task may be not yet started, started (or partially complete) or completed. The actual value may be determined by comparison of the status time (which is the point at which analysis is undertaken) with start and finish dates as below.  If StatusTime < ActualStart  THEN  IfcTaskStatusEnum := NotYetStarted  If StatusTime >= ActualStart  AND   StatusTime <= ActualEnd  THEN   IfcTaskStatusEnum := Started  If StatusTime > ActualEnd  THEN   IfcTaskStatusEnum := Completed	IfcTaskStatusEnum	see type	see type	NIL
OPT	IsCritical	A flag which identifies whether a scheduled task is a critical item within the programme.  NOTE - A work task becomes critical when the float time becomes zero or negative.	BOOLEAN	see type	see type	NIL

No formal and informal propositions defined at this level.

Interface Definitions

• I_WorkSchedule

Type Definitions

This class is not typed -- there is no type definition.

Class IfcWorkTask

EXPRESS Definition

Class Semantic Definition

An identifiable unit of work to be carried out independently of any other units of work. IfcWorkTask also has the capability of nesting, or being nested by, other work tasks, through the relationships to IfcRelNestsProcesses.

NOTE: New class in IFC Release 1.51 to enable the nesting of work tasks.

Attribute and Relationship Definitions

Inherited Classes

Attributes and Relationships

	Attribute / Relation	Definition	Data or Relation Type	Min	Max	Default
OPT	WorkTaskId	An identifying designation given to a task.	STRING	see type	see type	NIL
OPT	TaskDescription	A text description of the task to be undertaken as it appears in a Construction Plan.	STRING	see type	see type	NIL
OPT	TaskCost	The cost of carrying out a task.	IfcCost	see type	see type	NIL
OPT	WorkMethod	The method of work used in carrying out a task.	STRING	see type	see type	NIL
OPT	WorkTaskSchedulingData	The information about the time schedule of the task	IfcWorkSchedule	see type	see type	NIL

Formal Propositions:

WR31	Restrict the relationship 'Nests' inherited from IfcObject to IfcRelNestsProcesses.
WR32	Restrict the relationship 'IsNestedBy' inherited from IfcObject to IfcRelNestsProcesses.

Interface Definitions

• I_WorkTask

Type Definitions

This class is not typed -- there is no type definition.