Concurrency is Crucial to Beneficial BIM

February 4, 2016

Concurrency is Crucial to Beneficial BIM

With the UK government BIM level 2 mandate deadline fast approaching, the AEC sector continues to register mixed opinions as to its benefit on cost. According to Stephan Jones, Segment Manager at Trimble MEP, the government BIM level 2 definition has partially contributed to these differing perceptions by not promoting the central pillar of the standards as originally developed by the IAI (International Alliance for Interoperability) now rebranded as BuildingSmart.

A firm believer that the biggest prize in the BIM sweepstakes is concurrent working, Jones explains that were concurrency as a principle taken to an extreme, it would allow users to simultaneously manipulate the same information; perhaps a CAD model object, a property of that object, an associated cost or other BIM information facet.

“Likely you’ll probably be exclaiming that such a proposition is inherently chaotic and completely undesirable in the construction delivery context, but bear with me,” he says.

“If you have been exposed to systems such as Google docs or slides and have collaborated in the development of a presentation or commercial proposal then you may never wish to go back to a text editor on your isolated machine. I can attest it’s happened to me and I wouldn’t go back!

“Using Google’s collaboration tools you will notice that you no longer send files to each other, you don’t sit there wondering whether or not you are looking at the latest version, or whether you need to wait to add those other changes that just entered your consciousness.

“Construction delivery is riddled with the exact same experiences, only they are hugely magnified. Swap out the simple doc and replace it with a highly complex, multifaceted, detailed and interdependent BIM!” he explains.

“Standard data management techniques generally take a pessimistic approach to sharing, if you work on a network and share an Excel file you may have noticed that when it has already been opened by a colleague Excel warns you that you cannot edit information before you receive notice that the other user has closed the file, normally a source of frustration resulting in leaving the task you were going to do undone. Pessimism in this instance however is there to ensure that information is not and cannot ever be corrupted, a principle most of us are generally happy to endorse!”

“As you might expect, the computing world does offer up a second paradigm characterised as being optimistic. This allows multiple copies of the same information to be accessed and manipulated by more than one user; when the changes are saved the system uses techniques to attempt to merge the disparate changes,” he explains.

“Imagine a sentence edited by one user is wholly deleted by another, what results from the merge operation? It would be fairly chaotic if we have no semantic notion of what a ‘sentence’ is. Understanding what a sentence is, we might conclude that the sentence edits are only relevant in the context of the sentence and should therefore not be kept as a result of the merge process.

“The pessimistic approach does suggest that concurrent working can only succeed when a single shared data source exists. We would need to be simultaneously connected and wait for transactions to be committed one at a time. This approach can work quite well in simple scenarios where the transaction length is small and can be quickly processed. When dealing with BIM data the transaction length quickly becomes a serious bottleneck and untenable.

“Is the optimistic approach therefore the preferred solution to provide a platform for concurrency? Unfortunately, BIM does not at level 2 equal IFC (industry foundation classes, the standard for storing construction information). Remember we are happily using our proprietary files and at this stage in our evolution the data objects inside those files do not have semantic meanings. In simple terms nothing allows us to formally distinguish a toilet from a door or a work rate from a window, this becomes a problem as illustrated earlier (semantics). Classification systems are being used to circumvent the problem but they cannot substitute the need for more complete ontologies or semantic definitions that are inherent in the IFC schema.

“Whilst concurrency can positively impact the whole construction delivery process it is design production and management where concurrency has perhaps the biggest practical benefit”.

He adds: “Presently (within the context of PAS1192-1) designers are advised to adopt information segregation strategies, creating innumerable files to logically divide space and disciplines such that teams can function properly, of course it’s not limited to file names, depending on the system used, careful control of layer names also exist. Design managers actually need to consider and manage file names using multi-part codes that are hugely obscure for all but the most frequent of project participants.

“Designers across disciplines receive a common brief, often not co-located, they disperse and work in isolation for a period of time. In the future there is a need to integrate the design outputs and coordinate. If any margin for misinterpretation or misunderstanding exists, these will be reflected in the designs; the greater the time delay between coordination meetings the greater the extent of design issues, indicated as ‘amplitude of change’. The greater the amplitude the greater the level of rework.

“Concurrency also plays an important part in enabling change management, or ‘value engineering’ as it is commonly described. In simplistic terms the greater the cost of operating a design iteration the less benefit and therefore inclination there is to engage in the process. If the costs in undertaking design iterations can be reduced by for instance generating quantity revisions from a model rather than manually recalculating them, time is saved not just within the cycle but more widely across the supply chain and a projects’ mobilisation costs.”

“The final benefit of concurrency is that information is always up to date, you can trust it, you don’t have to search for it, what you need is there, what you see is the same as everyone else. Whether you are a designer, a client, a cost estimator, or a planner your calculations and views can be kept up to date enabling you to identify issues and react to change”, he concludes.


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