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IFC4 RV Objective

by courtesy of CAD Stelle Bayern


IFC4 Reference View

The IFC4 Reference View targets all work flows that are based on reference models. Read more:


Objective of the IFC4 Reference View

The main objective of the IFC Reference View is the widest possible proliferation of IFC BIM data across a big range of software application types supporting different communication and collaboration workflows.

The IFC Reference View is characterized by the ability to publish BIM data following that subset of IFC definitions that enables semantically rish content of building data, and to some degree also other built environment data, to be exchanges with a streamlined geometric representation that is optimized for analysis and display, but excludes dimension-driven geometric parameters. The geometric representation is therefore suitable for all workflow scenarios, where the imported IFC model is displayed, analysed, compared, clashed, but not parametricly modified for futher work processes.

Semantic building data models being exchanged using the IFC4 Reference View would typically include:

  • physical elements with explicit geometry, properties, quantities, material, and classification
  • types of elements with associated physical elements to group common definitions (geometry, properties, material, and classification)
  • spatial elements (spaces, zones) with explicit geometry, properties, quantities, and classification
  • spatial structure elements (site, building, story), but also spatial zones for non-vertical construction
  • element breakdown structure between physical elements (assemblies, sub-assemblies, parts)
  • spatial breakdown structure between spatial elements (spatial decomposition of building, story or zones)
  • spatial containment structure between spatial elements and physical elements (elements in spatial zone)
  • logical system structure and assignment (physical elements assigned to systems and sub systems)
  • topological structure of system networks (element to port, and port to port, relationship)
  • common context of the building model, providing units, coordinate system and GIS positions
  • general object identification using globally unique identifier

Additional capabilities for enriching the semantic information exposed by the IFC4 Reference View can be defined as an Add-on Model View Definition. Forseeable examples are capturing 4D models with the addition of the work schedule related entities, or 5D models with the addition of construction resource related entities.

Workflow support by the IFC4 Reference View

The overall goal of the IFC Reference View is to provide workflows where building information models are to be consumed by the widest array of software applications that do not require modifying geometry. Such applications enable viewing, estimating, building, operating, and other downstream analysis.


Figure: Reference model approach (by courtesy of Leon van Berlo, TNO)

EXAMPLE One target scenario is an architect providing building design information to a contractor or facility manager. It is expected that the resulting geometry would reflect sufficient realism for viewing in software (dimensions, normals, colors, textures), but not of rendering quality for artistic presentations (lighting, shader effects, curve interpolation, rasterizing).

To support the widest array of consuming applications, the resulting schema should be as limited as possible for representing geometry in the interest of minimizing resources required of application developers. Such schema should also be as compact as possible to enable downstream use on mobile devices with limited network bandwidth. It is proposed that the resulting geometry is limited to triangles with normal vectors, color and texture coordinates and simple sweept solids with applied color and texture.

Compatibility Concerns for the IFC4 Reference View

As the IFC4 Reference View is new (there is no corresponding concept in the IFC2x3 Coordination View), there is no constraint for compatibility, and the resulting schema will leverage new triangulation definitions in IFC4 to support more efficient data transfer.

The second Model View Definition that is proposed in parallel to the IFC4 Reference View, the IFC4 Design Transfer View, is an extension of this model view. In other words, the IFC4 Reference View is a true subset of the IFC4 Design Transfer View.

Complying software interfaces, that implements import of the IFC4 Design Transfer View, shall also be able to correctly import IFC4 Reference View data sets. But not vice versa, a complying software interface, that implements import of the IFC4 Reference View will not be capable to import IFC4 Design Transfer View data sets. It is however required that a compliant software interface for importing IFC4 Reference View displays an agreed error message showing the IFC version, and the IFC Model View Definition of the imported IFC file, that does not match "IFC4 Reference View" with an explanation, that a non-compatible IFC file has been received.

NOTE The correct error message and the link to further information on the buildingSMART website explaining the purpose of the different IFC Model View Definitions need to be agreed upon.
See next chapter Scope for more details.