Kolaboracja IFC

Secrets of the IFC format

The idea of open standards seems to be extremely important for technology development (including construction). The application of these standards is a driving force behind innovation. New technologies improve process efficiency, reduce costs, and speed up project delivery time. 

Where does the idea of open standards giving any results come from? There is no need to look far. Let’s have a look at the most recognizable example, a few people could imagine their everyday life without… the INTERNET.

The beginnings, as always, were rather difficult, but as users developed, certain inconveniences became apparent. Namely, the fact the websites had to be created multiple times to function properly in various browsers (Internet Explorer, Opera, etc.). Nowadays, regardless of the browser we use, their producers provide standard certificates allowing those who write web pages to share a common set of rules. By using open standards, computers around the world can easily interact with each other. Could you imagine it’s different? Well, that’s right. Definitely not.

In a previous article concerning IFC https://bimcorner.com/everything-worth-knowing-about-the-ifc-format/ among other things, the basics of IFC format, learn about the history of its creation and the easiest possible usage. However, what makes this format so universal, and why should it be widely used in BIM? I’ll try to answer this and some other questions in the following article today. Let’s start.

 

1. On IFC one more time.

IFC is a neutral, open format for data exchange, being the basis of the openBIM methodology – more about it here: https://www.graphisoft.com/archicad/open_bim/

What makes it so universal, though?

1.1 Semantic, namely common features

Its most prominent feature seems to be the fact it’s based on semantic definitions. What does it mean? Let’s consider the simple object which is a table. The table has certain features – it has a horizontal top and legs. Seeing an object with such features – a top and legs – we can say this object is a table. We don’t take into account all the features of a given object (such as color, since not all tables are the same), but we choose features common to all objects of a given set (horizontal top and legs).

1.2 IFC file object definitions

The IFC schema is structured to ensure that each unit in its structure has its own meaning.

Suppose we work with an architectural model of the building. We select an object, e.g. a door. This object is defined as IFCdoor in the IFC file classification: 

https://standards.buildingsmart.org/IFC/RELEASE/IFC4/FINAL/HTML/link/ifcdoor.htm

Definicja IfcDoor
Definition of IFCdoor (source: https://standards.buildingsmart.org/IFC/RELEASE/IFC4/FINAL/HTML/link/ifcdoor.htm )

“Doors are a building element that is primarily used for controlled access to people and goods. It includes hinged, revolving, sliding, and additionally rotatable and folding constructions. The door consists of a frame and one or several panels.”

Assigning a specific, standardized meaning to each element makes the IFC a semantic standard. Adhering to these definitions is, therefore, extremely important for the exchange of information between different programs. The idea is that each program should recognize the individual elements in the same manner. Thus, IFCdoor is a door, IFCwindow is a window, and consequently IFCstair is a staircase.

IFC defines all elements precisely, but you know – a description alone isn’t enough. It doesn’t matter, when exporting to IFC, the “door” element will be merely correctly identified as “IFCdoor”.

1.3 Attributes of IFC objects

The attributes assigned to them are also important from the engineer’s point of view (the door has a dimension, the material it’s made of, its position in space). IFC describes each element as a class. It may seem a bit confusing, but in a nutshell, the idea of each element is to have a list of attributes (name, material, position, dimensions) and the type of attribute value (text, number, coordinates, etc.).

It means the IFC creates a kind of template for each element having a precise definition along with a list of attributes (of course, the attributes are also precisely defined).

Atrybuty IfcDoor
List of atributes for IFC (source: https://standards.buildingsmart.org/IFC/RELEASE/IFC4/FINAL/HTML/link/ifcdoor.htm )

The export to IFC is thus a list of such templates in the form of a readable file available to other programs.

1.4 Structure, i.e. the tree of interconnections

The IFC isn’t composed of a flat structure with separate elements and their attributes, instead, it forms a tree of interconnections. What does it mean? Returning to the abovementioned “door” example (IFCdoor), the diagram fragment containing this item looks as follows:

All of these dependencies are defined in the IFC Schema – for more information see the following articles.

2. WHY IFC

2.1 Uniform scheme for organizing information in a file

This format was created for reliable data exchange among various programs. The majority of software has its way of data organization. Furthermore, throughout the project cycle, different types of programs are used by many users to achieve various results.

Tekla Structures Interfejs
Tekla Structures interface

The program for architects (e.g. Archicad) deviates from the program for steel constructors (Tekla Structures). The effect of an architect’s work also differs from that of a steel designer, and therefore the internal schemas through which the programs organize data vary widely.

Interfejs Archicad
ArchiCad interface (source: https://www.graphisoft.com/users/bim-case-studies/bim-technology-for-aura-apart.html)

For instance, the folder structure for the Tekla Structures model is as follows:

Folder modelu Tekla Structures
File structure in TEkla Structures model folder

In other words, it isn’t a single file but a file and folder structure.

In addition, new version updates also introduce new features, leading to changes in internal data organization, resulting in such information:

Or:

2.2 One universal plug-in for data exchange

The construction industry remains fragmented, with many professionals who have to work together and exchange information. Of course, it’s possible to create plug-ins for data exchange between various programs. This, in turn, creates thousands of links between the programs. Taking the above illustration into account, each time a program is updated, the plug-in would need to be updated, making it time-consuming and uneconomic. Right here, the IFC file comes to our help – one format, with a certain structure, with established semantic rules (it’s unambiguously determined what is and what is not, for example, the floor, or how doors and windows are defined).

3. Summary

What makes the open IFC format so flexible? Right, “openness” is the keyword and gold feature of IFC. IFC (Industry Foundation Classes) represents a standard that, alongside IDM (International framework of Dictionaries) and IDM (Industry Delivery Manual) constitutes the foundation of openBIM methodology.

openBIM, namely effective communication based on model data (IFC) using specific and standardized terminology (IFD), and common processes and methods (IDM) provides regulation for the development of the construction industry.

And are you already using IFC in your work? If so, share your thoughts in the comments section. What are the benefits and challenges of using IFC in your work?

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