iModel unleashed

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For over 10 years, iModel has been Bentley’s format for exchanging project information between design, construction and operations. It has expanded into a fundamental platform in its own right. But, what we didn’t expect, writes Martyn Day, was for Bentley to open source its development

Out of all the firms we cover in the industry, Bentley Systems is perhaps the most cautious and long-term developer we have seen. While others all around are changing their file formats with every other release, or buying applications and never integrating the technologies, I can only remember two file changes from Bentley in my lifetime and everything eventually works on the MicroStation backbone. With cofounder and CTO Keith Bentley still writing code and actively involved in the system architecture, the company just doesn’t do short-term software architecture.

iModel has become a growing differentiator for Bentley, with wide adoption in its base, as well as other AEC developers like Topcon, building an ecosystem of firms which actively want to share BIM data, despite being in competition.

At last month’s Year In Infrastructure (YII) event in London, iModel became even more important. It became the connection between all project participants and the hosted Digital Twin, though the new Bentley iTwin services offering, which connects Bentley’s iModel- Hub, with a Connected Data Environment (CDE). Attendees witnessed Microsoft, Siemens and Topcon all buying into the Azure hosted Digital Twin strategy.

Bentley Systems then announced iModel. js, an open source library to enable developers to incorporate web-based hooks that can bring in design and project data, which is stored in iModels on Bentley’s iModelHub. The idea being that any developer can now opt to use the iModel wrapper to integrate 2D, 3D, 4D and documents into custom cloud applications or services.

iModelHub is secure, so permission is always required to access the model data, but developers or customers will be free to ‘iModel enable’ any application they want. Customers of custom web applications that wish to use iModel will have to take up an iTwin subscription with Bentley to host the data.

Bentley picked Java as it is the most flexible standard for modern cloud and web development. It is written in TypeScript and leverages open technologies including SQLite, Node.js, NPM, WebGL, Electron, Docker, Kubernetes, and of course HTML5 and CSS. The same codebase can produce cloud services and web, mobile, and desktop applications. The source code is hosted on GitHub, a platform for hosting software code — especially open-source projects — and is distributed under the MIT licence. GitHub was recently bought by Microsoft for $7.5 billion.


By opting for an open source deployment, developers are also free to alter the code and Bentley will have to do the job of policing and maintaining its open development platform, as well as collating wish lists and changes which it will incorporate.

Keith Bentley explained that “by opensourcing the libraries we use to create our ‘iTwin’ cloud services, we expect to foster a substantial and vibrant ecosystem of innovation.” Clearly this is a play for Bentley to drive the standard into the burgeoning cloud-development fraternity, who have very few tools to integrate complex BIM data into their solutions.

iModel is not providing developers with a dumb viewer of 3D files, but a powerful suite of tools that can interrogate a staggering array of project information and metrics, including project history and changes. In short, adopting iModel.js gives access to the iModelHub and opens a window into the live Digital Twin data in a completely web friendly way, and at no cost to the developer.

Keith Bentley told AEC Magazine that the development landscape has changed and, with the Googles and GitHubs of this world, development tools are predominantly free. He posed the question, how would you get a developer interested in using your tools if there was an upfront cost to become an accredited developer?

Bentley also explained that as a programmer it’s more exciting to get tools which you can look into and edit as you wish. The net result will be something interesting, he said, adding that by giving iModel.js away as open source, he hopes to proliferate the format but also enable innovation in our space.

One example of how iModel.js could be used was given by Shenzhen Expressway Consulting Group, which already uses iModelHub and sees a use of iModel.js for crafting a custom web-based tool for digital handover, after the completion of a project. It would enable visual operations and maintenance, feeding from data stored in its own iModelHub. Any changes made and documented by the company post-handover would also be immediately updated online.

Tracking origins

As with all Bentley innovations, it’s worth recapping on what the company delivered last year, to make iModel even more powerful. Bentley has always had a passion for trying to capture history and provenance of project changes. It has delivered a number of capabilities over time to capture the delta in model revisions.

Last year’s innovation brought this passion to iModel with the introduction of the iModelHub. When deployed, the Hub will capture all the changes that happen in a project’s lifecycle in an unalterable timeline. Just as accounting systems track money in and out, iModelHub provides digital security to identify what changed when and by whom. It’s a journal of record and could be invaluable to identify in projects when problems occurred. With a machine learning hat on, that could be valuable data to use in predicting problems on other projects in the future, but we will come back to that later.

iModels can now hold this data too. The cloud is where the changes are stored but everyone using iModels could theoretically get access to the project timeline. It’s safe, as the master is held in the cloud and the local instances are just synchronised. This also works with non-Bentley products, for which it has written ‘Bridges’, so the data is collated and added to the iModelHub timeline. This capability is unique in our industry and is yet another powerful iModel benefit. It’s similar to blockchain to a certain degree, although the authentication chain is online, and stored in one place, not in every iModel file.

Digital Twin

Digital Twin has to be the phrase of the moment. People have almost stopped using the word BIM and now seamlessly drop ‘Digital Twin’ in as a replacement. In many respects we welcome the substitution, as BIM is utterly meaningless outside of the gleaming digital spires of our enlightened object-oriented castles.

Digital Twin is short, simple and gives a glimmer of hope that the uninitiated would have some clue as to what we are on about. In the space of one month, I’ve heard Digital Twin on the mainstage at Bentley, Autodesk and Trimble events, as well as from Microsoft, Topcon and others.

According to Keith Bentley, it was completely serendipitous that both Microsoft and Bentley were pursuing the same track. Microsoft has been focusing on the construction space for a couple of years, everything from BIM to Digital Cities and IoT. It has been working on layers of machine learning which reside in the Azure cloud and have been used to learn from big data caches on the city scale. Bentley explained to us, “It sounds like we have been working on this for a while together but it was only when we talked about it that we discovered they had a Digital Twin strategy.”

As Bentley is almost a 100% Microsoft-based company, its choice of Azure for cloud storage will also benefit, in time, from Microsoft’s focus on machine leaning in the space. If the data is hosted on Azure, special built environment-centric analysis tools are in the works from both Bentley and Microsoft. Autodesk won’t benefit from this partnership as its customers’ data is hosted on Amazon Web Services.


iModel.js is a big technology story from Bentley’s stand point. For fear of calling the company a control freak, it would have been a huge surprise for it to open source anything, let alone something so fundamental to project collaboration.

Bentley is looking to gain traction and proliferate its formats. It realises that there is a lot of web-based development yet to happen in this space and by lowering the barrier to entry and being open about who uses it, it might find it has an advantage over our traditional proprietary industry mindsets.

The other benefit is that Bentley doesn’t have to create all the tools that customers want. It’s now possible for customers to create their own solutions and leverage their investment in Bentley back-end technology.

From this year’s YII, there was an overpowering feeling of momentum behind Bentley’s vision of Digital Twins and iModel. For years, Bentley Systems has been Microsoft’s biggest, best and most loyal AEC developer, but had benefitted little from this.

In the past, Microsoft people who covered the AEC space didn’t seem to be fully switched on, as to trends in the industries or the technologies that were in play. The Microsoft people we met at YII were a completely different class to those we have met before, showing a deep knowledge of IoT, BIM, Digital Twins, as well as properly understanding what Bentley has developed. Topcon too has really closely partnered with Bentley and is certainly speaking from the same page.

The elephant in the room was Siemens — Bentley’s giant development buddy, who is increasingly looking to focus on the AEC space. Bentley is integrating into Siemens’ uber document management system, Teamcenter, and even licensing technology to Siemens.

Keith Bentley told us that he likes the partnership as it is, the companies talk the same language and have little overlap, and it’s certainly helping their combined efforts in Power and Governmental customers. One wonders how long the engagement goes on before there is a marriage.

What is an iModel?

An iModel is a Bentley authored model and project data exchange format specifically designed to work in the lifecycle of infrastructure assets. It’s not just a CAD file. Essentially, it’s a wrapper for a multitude of data types: business properties, geometry, graphics, and relationships. This means a whole project can be contained within one file, irrespective of how many sources the original data came from.

Unlike proprietary formats, iModel is open and can be used by many competitive infrastructure developers.

The format is very efficient, crushing giant files, and designed for today’s cloud-based and mobile workflows. They are secure and play well with serverlevel security.

Additional information can be added to the iModel without impacting the data originally contained within it, great for lifecycle data capture tasks.

As of last year, iModels can also contain all the history of changes that have happened in a project’s lifetime when used in conjunction with Bentley iModelHub.

iModels can be created with Bentley products, as well as those from other sources, including PDMS, Revit, AutoCAD, Rhino, ArchiCAD, IFC, JT (plug-in) to name but a few. iModels can be filtered prior to crea – tion, limiting what data is exposed.

iModels can be used for many tasks: viewing 2D, 3D data, review (desktop or on mobile), access ODBC data, spreadsheets, reports, clash detection and now as a container for access to Digital Twin models.

iModel.js will mean that Digital Twin assets can be utilised in custom web applications. As iModel.js is open source, the capabilities are also expected to expand with input from the wider community.

Investing in machine learning and IoT

One of the big surprises at YII (it also surprised some Bentley employees) was the under the radar announcement that Bentley had acquired machine learning and IoT development company AIworx.

Keith Bentley gave us some background to the acquisition and the importance of machine learning going forward, “It came together very quickly, they are a great talented group of smart guys,” he said. “I’d guess in today’s terms it would be described as an ‘acqui-hire’ — we bought the company for the talent, as they don’t actually have any products.

“We had an ‘AI’ summit and invited some CIOs to shoot around ideas and the most common answer is, ‘we just want an easy button for my project’.

“In reality, firms need help to not repeat mistakes and to fine tune their performance, which is reasonable if you have enough data.

“Last year we asked firms if they would like to contribute their project data (iModelHub), but we didn’t get a whole lot of traction but this year we asked again and there seems to be a more positive reaction to pooling data, so we can machine learn. The problem now is going to be narrowing down the development opportunities,” he said.



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