technically feasible process, willpower required

Is it possible to write an article about IFC without going into technical details? We try to do it with the intention of communicating to readers that if one wants (where “yes” is deliberately impersonal because it involves a large community of actors), it is now technically possible to exchange BIM models of infrastructural works in IFC open format. The purpose of this article is to illustrate what is currently available, how to use it, and what happened to make this opportunity a reality.

A prerequisite is needed: this article is aimed at readers who know the BIM method, who know what IFC is, and who recognize the impact of an open BIM approach on its application. To ensure fluid information, it is impossible to ignore the correct use of the IFC format; in terms of key concepts in the method such as “sharing” and “interoperability”, the IFC plays a crucial role. Readers responding to the above premise also know that the IFC standard was previously unable to allow an accurate semantic and geometric description of linear infrastructures evolving along a path. This article, which is divided into five sections, describes the new IFC standard available to date and how it supports the exchange of openBIM models of infrastructural works.


IFC 4.3 will be the new version of the ISO 16739 standard within the first quarter of ’23

IFC 4.3which is the latest version of IFC created by buildingSmart International and available to cover the domains of railways, roads, bridges and ports, has entered the ISO path. The plan expects it to be the new version of the ISO 16739 standard in the first quarter of 2023. This plan is feasible thanks to a memorandum of understanding signed between buildingSmart International and ISO, which provides for the establishment and maintenance of standards for openBIM within the international buildingSmart association and their approval of ISO in a more streamlined and faster way than usual. In cascade, CEN and UNI will implement the ISO standard.

Source: https://www.iso.org/standard/70303.html

The IFC version sent to ISO can be downloaded from row “4.3.0” in the table on the buildingSmart International website.

The row “IFC4.3.1 dev” in the table instead collects the modifications of IFC 4.3, which will then be “frozen” in the IFC 4.4 or IFC 5 versions. As you can see, the IFC format, as well as many other standards produced, are constantly evolving. The improvement of the standard over time, the presence of companies ready to invest in the development of this standard and the availability of organizations dedicated to its maintenance only increase the robustness and reliability of the standard itself.

Second point: IFC 4.3 has been thoroughly tested and shown that it does not know everything, but it can do a lot, which is very different from small. IFC 4.3 is the result of a multi-year international process carried out by two major buildingSmart projects: IFCRail and IFCInfra. The only project IFCRail received a loan of € 4.6 million of railway infrastructure managers and design companies. These topics captured their information requirements and left them to a technical support group who understood them and as a result worked on the definition of IFC 4.3.

Subsequently, they verified, according to precise validation rules, that the information requirements could be captured within IFC 4.3 models. Italy, through the participation of RFI and the support of Italferr, has played a fundamental role in this process.

Within the project, the tests took place according to a V-shaped approach typical of system engineering. Left leg of V presents the definition of the requirements to be tested, starting from complex realistic projects and cases (history line), up to detailed requirements, with a limited scope (unit test). The right leg of the V contains the validation process, which actually starts from the unit tests up to the stories.

IFC 4.3 test - access

Figure 2: IFC 4.3 Test access

In the IFCRail project alone, there are 37 unit testsdivided into 7 items (or items): tracks with superelevation, linear positioning, solidly constructed by extrusion of an area, spatial structure, degradation of systems, doors and connections, physical elements of railway domain.

IFC 4.3 Test - Arguments tested

Figure 3: IFC 4.3 Test – Arguments tested

They have also been tested 10 stories, ranging from the executive design of a high-speed line to the acquisition and modernization of an existing line (the latter by RFI and Italferr). The tests took place through accurate definition of validation rules and production of models in IFC 4.3 format by some software houses. And this paves the way for the third point of this article.

Third point: IFC 4.3 has already been implemented. Some software houses make it already available, others include development in their future roadmap. The progress of the software houses was supported and tracked within Implementer Forum Rail and Infra, again in connection with the buildingSmart International projects. Only in the IFCRail project have they been produced in addition 120 reference IFC 4.3 filesand the software houses have shared about 50.

    IFCRail Implementor Forum - Participants

Figure 4: IFCRail Implementor Forum – Participants

The Implementor Forums represented an opportunity to complete the IFC 4.3 standard and support software houses in its implementation. Also in this case, Italy was the main character with two national software houses that were very active in the implementation of IFC 4.3: ACCA and Sierrasoft.

Fourth point: an MVD is already available for IFC 4.3. MVD stands for Model View Definition: it represents a subset of the entire IFC standard, selected for a specific purpose. In general, MVDs have hitherto been used to certify software for the import and export of IFC models, to detail the information requirements for data exchange (therefore mentioned in the information specifications) and to stop the export of IFC files in BIM authoring software. We assure the reader to choose the right MVD for IFC 4.3: at the moment there is only one available and it is called Alignment Based Reference View.

Fifth point: bSI will soon make the program available for IFC 4.3 software house certification. The tests to be passed to obtain certification are already ready and include the models to be produced, the expected results and the validation criteria.

As we would like to show: today it is technically possible to exchange BIM models of infrastructure works in the open IFC format. We have an ISO standard, tested and implemented.

The time has come for the whole of society to take action to make this opportunity a reality. How to do this given the recent development phase of the standard? Large builders can start rewarding the use of IFC 4.3 in tenders. Those responsible can start sending IFC 4.3 models to their customers, even if IFC is not required. Educators, facilitators and consultants need to update their knowledge and content to include IFC 4.3. Software houses can use the IFC 4.3 implementation as an opportunity to add value to their software.

There is a lot to do, but anything is technically possible.

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