IFC Schema Error Reference

Quick Reference

Decision Tree: Schema Error Diagnosis

Error when using IFC entity or attribute?
├── RuntimeError: entity "XYZ" not found
│   ├── Entity exists in a DIFFERENT schema version?
│   │   ├── YES → Check model.schema, use version-aware class name
│   │   │   ├── IfcBuildingElement → IFC4X3 uses IfcBuiltElement
│   │   │   ├── IfcWallStandardCase → IFC4X3 removed, use IfcWall
│   │   │   ├── IfcDoorStyle → IFC4+ uses IfcDoorType
│   │   │   └── IfcWindowStyle → IFC4+ uses IfcWindowType
│   │   └── NO → Entity does not exist in ANY schema
│   │       └── Check spelling and IFC specification
│   │
│   └── Entity is IFC4X3-only (infrastructure)?
│       └── IfcRoad, IfcBridge, IfcRailway, IfcAlignment, etc.
│           → ONLY available in schema="IFC4X3"
│
├── AttributeError: entity has no attribute "XYZ"
│   ├── PredefinedType on IFC2X3 elements?
│   │   └── Most elements lack PredefinedType in IFC2X3
│   ├── OwnerHistory is None in IFC2X3?
│   │   └── OwnerHistory is REQUIRED in IFC2X3, OPTIONAL in IFC4+
│   └── Attribute renamed between versions?
│       └── Check attribute change table below
│
├── Need to migrate between schema versions?
│   └── Use ifcpatch Migrate recipe
│       ├── IFC2X3 → IFC4: ifcpatch.execute({...recipe: "Migrate", arguments: ["IFC4"]})
│       └── IFC4 → IFC4X3: ifcpatch.execute({...recipe: "Migrate", arguments: ["IFC4X3"]})
│
└── Schema mismatch when combining files?
    └── ALWAYS check model.schema before transferring entities
        └── Use model.add(entity) ONLY between same-schema files

Critical Warnings

• ALWAYS check model.schema before using schema-specific entities. NEVER assume the schema.
• NEVER use IfcBuildingElement in IFC4X3 code — it was renamed to IfcBuiltElement.
• NEVER use IfcWallStandardCase or any *StandardCase entity in IFC4X3 — they were all removed.
• NEVER use IfcDoorStyle or IfcWindowStyle in IFC4+ code — use IfcDoorType and IfcWindowType.
• ALWAYS provide OwnerHistory when creating entities in IFC2X3 files (it is REQUIRED).
• NEVER transfer entities between files of different schemas without migration.
• ALWAYS use ifcopenshell.api.run() for entity creation — it handles schema differences automatically.
• ALWAYS validate IFC files after schema migration with ifcpatch.

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Essential Error Patterns

Error 1: Entity Not Found — Schema Version Mismatch

Symptom: RuntimeError when calling model.by_type() or model.create_entity() with an entity name that does not exist in the file's schema.

# WRONG: IfcBuiltElement does not exist in IFC2X3 or IFC4
model = ifcopenshell.open("legacy_building.ifc")  # schema = "IFC2X3"
elements = model.by_type("IfcBuiltElement")  # RuntimeError!

# WRONG: IfcBuildingElement does not exist in IFC4X3
model = ifcopenshell.open("new_infra.ifc")  # schema = "IFC4X3"
elements = model.by_type("IfcBuildingElement")  # RuntimeError!

Fix: ALWAYS check model.schema and use the correct entity name.

# CORRECT: Version-aware entity class selection
schema = model.schema
if schema == "IFC4X3":
    building_element_class = "IfcBuiltElement"
else:  # IFC2X3, IFC4
    building_element_class = "IfcBuildingElement"
elements = model.by_type(building_element_class)

Error 2: StandardCase Entity Not Found in IFC4X3

Symptom: RuntimeError when querying IfcWallStandardCase, IfcBeamStandardCase, etc. in an IFC4X3 file.

IFC4 introduced 11 *StandardCase subtypes. IFC4X3 removed all of them, merging behavior back into parent classes.

Removed in IFC4X3:

• IfcBeamStandardCase → use IfcBeam
• IfcColumnStandardCase → use IfcColumn
• IfcDoorStandardCase → use IfcDoor
• IfcMemberStandardCase → use IfcMember
• IfcOpeningStandardCase → use IfcOpeningElement
• IfcPlateStandardCase → use IfcPlate
• IfcSlabStandardCase → use IfcSlab
• IfcSlabElementedCase → use IfcSlab
• IfcWallElementedCase → use IfcWall
• IfcWindowStandardCase → use IfcWindow

# CORRECT: Version-safe wall query
schema = model.schema
if schema == "IFC2X3":
    walls = model.by_type("IfcWallStandardCase")
elif schema == "IFC4":
    walls = model.by_type("IfcWallStandardCase")  # exists in IFC4
else:  # IFC4X3
    walls = model.by_type("IfcWall")  # StandardCase removed

Error 3: IFC4X3-Only Entities on Older Schemas

Symptom: RuntimeError when creating infrastructure entities on IFC2X3 or IFC4 files.

# WRONG: IfcRoad only exists in IFC4X3
model = ifcopenshell.file(schema="IFC4")
road = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcRoad", name="Highway")  # RuntimeError!

IFC4X3-only entities (partial list):

• Facilities: IfcFacility, IfcBridge, IfcRoad, IfcRailway, IfcMarineFacility
• Facility parts: IfcFacilityPart, IfcBridgePart, IfcRoadPart, IfcRailwayPart, IfcMarinePart
• Infrastructure: IfcAlignment, IfcBearing, IfcCourse, IfcKerb, IfcPavement, IfcRail, IfcTrackElement
• Geotechnical: IfcGeotechnicalElement, IfcBorehole, IfcGeomodel
• Other: IfcDeepFoundation, IfcLinearElement, IfcTransportationDevice

Fix: ALWAYS create IFC4X3 files for infrastructure projects.

# CORRECT: Use IFC4X3 for infrastructure
model = ifcopenshell.file(schema="IFC4X3")
road = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcRoad", name="Highway")  # Works

Error 4: OwnerHistory Required in IFC2X3

Symptom: Invalid IFC2X3 file — OwnerHistory is $ (null) but IFC2X3 requires it on all IfcRoot subclasses.

# WRONG: OwnerHistory is REQUIRED in IFC2X3
model = ifcopenshell.file(schema="IFC2X3")
wall = model.createIfcWall(
    ifcopenshell.guid.new(),
    None,  # OwnerHistory = None → INVALID in IFC2X3!
    "MyWall"
)

Fix: Use ifcopenshell.api.run() which handles OwnerHistory automatically, or provide it explicitly.

# CORRECT: api.run() handles OwnerHistory for all schemas
wall = ifcopenshell.api.run("root.create_entity", model,
    ifc_class="IfcWall", name="MyWall")

# CORRECT: Manual creation with explicit OwnerHistory
owner_history = ifcopenshell.api.run("owner.create_owner_history", model)
wall = model.createIfcWall(
    ifcopenshell.guid.new(),
    owner_history,  # REQUIRED in IFC2X3
    "MyWall"
)

Error 5: IfcDoorStyle / IfcWindowStyle vs IfcDoorType / IfcWindowType

Symptom: RuntimeError when querying IfcDoorType in IFC2X3, or IfcDoorStyle in IFC4X3.

Type Entity	IFC2X3	IFC4	IFC4X3
IfcDoorStyle	YES	Deprecated	REMOVED
IfcWindowStyle	YES	Deprecated	REMOVED
IfcDoorType	NO	YES	YES
IfcWindowType	NO	YES	YES

# CORRECT: Version-safe type class selection
def get_door_type_class(schema):
    if schema == "IFC2X3":
        return "IfcDoorStyle"
    return "IfcDoorType"  # IFC4, IFC4X3

def get_window_type_class(schema):
    if schema == "IFC2X3":
        return "IfcWindowStyle"
    return "IfcWindowType"  # IFC4, IFC4X3

Error 6: PredefinedType Not Available in IFC2X3

Symptom: AttributeError when accessing element.PredefinedType on IFC2X3 entities that lack this attribute.

Many entities gained PredefinedType in IFC4 that did not have it in IFC2X3: IfcBeam, IfcColumn, IfcDoor, IfcWall, IfcWindow, IfcSlab, and others.

# WRONG: Assumes PredefinedType exists (fails on IFC2X3 IfcBeam)
for beam in model.by_type("IfcBeam"):
    print(beam.PredefinedType)  # AttributeError in IFC2X3!

# CORRECT: Check schema or use hasattr
for beam in model.by_type("IfcBeam"):
    if hasattr(beam, "PredefinedType"):
        print(beam.PredefinedType)
    else:
        print("No PredefinedType (IFC2X3)")

Error 7: IfcContext Does Not Exist in IFC2X3

Symptom: RuntimeError querying IfcContext in IFC2X3. In IFC2X3, IfcProject inherits from IfcObject. In IFC4+, IfcProject inherits from IfcContext (new abstract class).

# WRONG: IfcContext does not exist in IFC2X3
project = model.by_type("IfcContext")  # RuntimeError in IFC2X3!

# CORRECT: Use IfcProject directly (works in all versions)
project = model.by_type("IfcProject")[0]

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Schema Migration with ifcpatch

Migration Recipe

The Migrate recipe in ifcpatch converts IFC files between schema versions. Upgrading is more reliable than downgrading.

import ifcopenshell
import ifcpatch

# Upgrade IFC2X3 → IFC4
model = ifcopenshell.open("input_2x3.ifc")
output = ifcpatch.execute({
    "input": "input_2x3.ifc",
    "file": model,
    "recipe": "Migrate",
    "arguments": ["IFC4"]
})
ifcpatch.write(output, "output_ifc4.ifc")

# Upgrade IFC4 → IFC4X3
model = ifcopenshell.open("input_ifc4.ifc")
output = ifcpatch.execute({
    "input": "input_ifc4.ifc",
    "file": model,
    "recipe": "Migrate",
    "arguments": ["IFC4X3"]
})
ifcpatch.write(output, "output_ifc4x3.ifc")

Migration Limitations

• The Migrate recipe is experimental — ALWAYS validate output.
• Upgrading (IFC2X3 → IFC4 → IFC4X3) is more stable than downgrading.
• Entity renames are handled automatically (IfcBuildingElement → IfcBuiltElement).
• StandardCase merging is handled automatically.
• Custom property sets are preserved.
• Geometry may require manual review after migration.
• ALWAYS compare entity counts before and after migration.

Post-Migration Validation

import ifcopenshell
import ifcopenshell.validate

model = ifcopenshell.open("migrated.ifc")
logger = ifcopenshell.validate.json_logger()
ifcopenshell.validate.validate(model, logger)

for error in logger.statements:
    print(f"{error['severity']}: {error['message']}")

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Entity Availability Quick Reference

Entities That Changed Name

IFC2X3	IFC4	IFC4X3
IfcBuildingElement	IfcBuildingElement	IfcBuiltElement
IfcBuildingElementType	IfcBuildingElementType	IfcBuiltElementType
IfcDoorStyle	IfcDoorType (new)	IfcDoorType
IfcWindowStyle	IfcWindowType (new)	IfcWindowType

Entities Removed in IFC4 (from IFC2X3)

• IfcBezierCurve → use IfcBSplineCurve
• IfcRationalBezierCurve → use IfcBSplineCurve
• Ifc2DCompositeCurve → use IfcCompositeCurve
• IfcCalendarDate, IfcLocalTime, IfcDateAndTime → use IfcDateTime (string)
• IfcMove → use IfcTask
• IfcOrderRequest → use IfcTask
• IfcRelAssignsTasks → use IfcRelAssignsToProcess
• IfcElectricDistributionPoint → use IfcElectricDistributionBoard

Entities Removed in IFC4X3 (from IFC4)

All StandardCase subtypes:

• IfcBeamStandardCase, IfcColumnStandardCase, IfcDoorStandardCase
• IfcMemberStandardCase, IfcOpeningStandardCase, IfcPlateStandardCase
• IfcSlabStandardCase, IfcSlabElementedCase, IfcWallElementedCase
• IfcWindowStandardCase
• IfcPresentationStyleAssignment → use IfcStyledItem directly

Attribute Changes Across Versions

Entity	Attribute	IFC2X3	IFC4+
IfcRoot	OwnerHistory	REQUIRED	OPTIONAL
IfcMaterial	Description, Category	Not available	OPTIONAL
IfcStairFlight	NumberOfRiser	Singular	NumberOfRisers (plural)
IfcBuildingElementProxy	CompositionType	Present	Replaced by PredefinedType
IfcRelSequence	LagTime	float	TimeLag (IfcLagTime object)
Most elements	PredefinedType	Not available	OPTIONAL
Date/Time fields	—	IfcDateAndTime objects	IfcDateTime strings

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Schema Introspection

Checking Entity Existence at Runtime

import ifcopenshell

def entity_exists_in_schema(schema_name, entity_name):
    """Check if an entity exists in a specific IFC schema."""
    schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(schema_name)
    try:
        schema.declaration_by_name(entity_name)
        return True
    except RuntimeError:
        return False

# Usage
print(entity_exists_in_schema("IFC2X3", "IfcBuiltElement"))  # False
print(entity_exists_in_schema("IFC4X3", "IfcBuiltElement"))  # True
print(entity_exists_in_schema("IFC4X3", "IfcBuildingElement"))  # False

Listing Entity Attributes Per Schema

schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name("IFC4")
entity = schema.declaration_by_name("IfcWall")
for attr in entity.all_attributes():
    print(f"{attr.name()}: {attr.type_of_attribute()}")

---

Version-Safe Coding Patterns

Pattern: Universal Building Element Query

def get_building_elements(model):
    """Get all building/built elements regardless of schema version."""
    schema = model.schema
    if schema == "IFC4X3":
        return model.by_type("IfcBuiltElement")
    return model.by_type("IfcBuildingElement")

Pattern: Safe Entity Creation with Schema Check

def create_entity_safe(model, ifc_class, **kwargs):
    """Create entity with schema validation."""
    schema = ifcopenshell.ifcopenshell_wrapper.schema_by_name(model.schema)
    try:
        schema.declaration_by_name(ifc_class)
    except RuntimeError:
        raise ValueError(
            f"Entity '{ifc_class}' does not exist in {model.schema}. "
            f"Check the schema version compatibility."
        )
    return ifcopenshell.api.run("root.create_entity", model,
        ifc_class=ifc_class, **kwargs)

Pattern: Schema-Agnostic Utilities

ALWAYS prefer ifcopenshell.util functions over manual traversal — they handle schema differences internally:

import ifcopenshell.util.element

# These work identically across IFC2X3, IFC4, and IFC4X3:
container = ifcopenshell.util.element.get_container(element)
psets = ifcopenshell.util.element.get_psets(element)
material = ifcopenshell.util.element.get_material(element)
element_type = ifcopenshell.util.element.get_type(element)

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Reference Links

• API Method Signatures — Schema introspection and migration methods
• Working Code Examples — Version-safe coding patterns
• Anti-Patterns — Schema-related mistakes and fixes