Module Contents

ifcopenshell.api.sequence.assign_process.assign_process(file, relating_process=None, related_object=None) None

Assigns an object to be related to a process, typically a construction task

Processes work using the ICOM (Input, Controls, Outputs, Mechanisms) paradigm in IFC. This process model is commonly used in modeling manufacturing functions.

For example, processes (such as tasks) consume Inputs and transform them into Outputs. The process may only occur within the limits of Controls (e.g. cost items) and may require Mechanisms (ISO9000 calls them Mechanisms, whereas IFC calls them resources, such as raw materials, labour, or equipment).



+——–+ +———+ +———+ | Inputs | –> | Process | –> | Outputs | +——–+ +———+ +———+


There are three main scenarios where an object may be related to a task: defining inputs, controls, and resources of a process.

For inputs, a product (i.e. wall) may be defined as an input to a task, such as when the task is to demolish the wall (i.e. the wall is an input, and there is no output).

For controls, a cost item may be defined as a control to a task.

For resources, any construction resource may be assigned to a task.

  • relating_process (ifcopenshell.entity_instance) – The IfcProcess (typically IfcTask) that the input, control, or resource is related to.

  • related_object (ifcopenshell.entity_instance) – The IfcProduct (for input), IfcCostItem (for control) or IfcConstructionResource (for resource).


The newly created IfcRelAssignsToProcess relationship

Return type:



# Let's imagine we are creating a construction schedule. All tasks
# need to be part of a work schedule.
schedule = ifcopenshell.api.run("sequence.add_work_schedule", model, name="Construction Schedule A")

# Let's create a construction task. Note that the predefined type is
# important to distinguish types of tasks.
task = ifcopenshell.api.run("sequence.add_task", model,
    work_schedule=schedule, name="Demolish existing", identification="A", predefined_type="DEMOLITION")

# Let's say we have a wall somewhere.
wall = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcWall")

# Let's demolish that wall!
ifcopenshell.api.run("sequence.assign_process", model, relating_process=task, related_object=wall)