The BIM Lexicon Problem
Why language is a problem for BIM
TL;DR: There has been confusion surrounding the term in BIM and it's meaning, leading to a move towards using the term Information Management in the UK. BIM is also divided into levels of maturity and dimensions, with each additional dimension representing the addition of more information to the model. However, these terms have caused confusion and misunderstandings when used for specification. It's more important to SAY WHAT YOU MEAN than to use BIM terminology.BIM has always had a language problem. The very name Building Information Modelling has been confused and conflated with other terms to fit the acronym - Building Information Management, and 'Better Information Management’.
The meaning of BIM itself has never really been defined well over the industry - to some its 3D modelling, to others it’s using Autodesk BIM360(!), to others it’s a digital building collaboration and management process.
This is why I believe that in the UK there is a definitive move towards the term Information Management, reflecting the shift in focus of UK government and industry discussion about digital transformation in the built environment since 2016.
The effect of all this is confusion. We have 1.4million workers in construction - to realise the benefits that Information Management can bring we need to extend a consistent message to all.
Given the enormity of what we tackle it’s not surprising that we’ve ended up with some shorthand in the BIM lexicon, and that is what I want to deconstruct today - specifically 4D,5D,6D and on, and BIM maturity levels.
Maturity Levels
BIM levels were expressed in the below Bew-Richards BIM maturity diagram, better known as the “BIM wedge”, published originally in 2008.
Whilst incredibly useful to define the maturity development, more of a roadmap really, it was an attempt to take the ambiguity out of ‘BIM’ and show the categories of collaboration and technical expectations. Under PAS1192-2 this was a tool used by some clients to specify their BIM requirements - “we want BIM Level 2”.
Whilst useful at the time, a time when BIM maturity was at an industry low, things have moved on. It is now recognised that simply stating “we want BIM Level 2” is nowhere near clear enough.
With the advent of ‘BIM according to ISO19650’, and growing industry maturity, it is clear that there needs to be much more definition to specification of information requirements. The UK BIM Framework guidance is a fantastic reference to guide the development of and response to information requirements.
However, I’m still seeing this old phrasing in customer Exchange Information Requirements (EIR) which also specify ISO19650-2, this is a contradiction. As we’ll see later, this has issues on multiple levels in the delivery and management of information. Producers are unclear what they’re contracted to provide, customers are unclear on what to expect.
Multidimensional
Since the advent of CAD 3D modelling there has been a need to differentiate between 2D and 3D processes and outputs. As ‘BIM’ use cases and processes developed in construction the ‘dimensions’ then grew. For clarity I will use the NBS definitions for the below but, and this is a key point, definitions vary between sources.
‘BIM Dimensions’
2D BIM
2D BIM is a digital geometric model that constitutes an X and a Y axis associated with further information.
3D BIM
3D BIM is a digital geometric model that constitutes an X, Y and Z axis associated with further information.
4D BIM
4D BIM is adding scheduling information to model construction sequences.
5D BIM
5D BIM is generally considered to be adding cost information to a model.
6D BIM
6D BIM is considered by some to be adding facility management to the information set.
7D BIM
7D BIM is considered by some to be adding sustainability information to the information set.
8D BIM
8D BIM is considered by some to be adding health and safety information to the information set.
Useful, to an extent
The evolution of these terms has been driven by an industry need. Due to the lagging maturity of BIM in the industry and the complexity beneath some of the processes and use cases, short-hand terms are useful to summarise whole areas of ‘BIM’. It’s easier to raise awareness as a whole by teaching the majority on short-hand terms - “4D is a model which runs like a video showing the programme of works”.
Unfortunately though, these terms have been used for more than just short-hand and awareness. They’ve been used for specification.
So what?
The problem using the BIM levels and dimensions to specify requirements are that:
Poor definition; Some of the terms don’t have an agreed upon definition. It depends which source you take the definition from.
Outdated; in terms of BIM levels this is a fundamentally outdated principal which is superseded by the latest standards, the ISO19650 series.
False comfort; the simple use of a short-hand terms can give the false impression that thinking has taken place to the uninitiated, but in reality the use of these terms actually blocks specific thinking.
Poor delivery; ultimately, they can’t be delivered to. Even saying 2D or 3D requires further definition of requirements, standards, and processes.
The outcome of this is ambiguity. Unless picked up early by the recipient of the specification (EIR), it is unclear to both the receiving and producing party what is required - therefore,the baseline is not clear.
Ambiguity causes arguments
One of the biggest issues we have in successful implementation of Information Management in construction today is a lack of clarity on what is expected early enough in the process.
In my experience where there is ambiguity in the requirements, dependant on the the relationship between parties, it’s very likely that disagreements and protracted discussion will ensue. This increases costs, produces abortive work and rework, ultimately increases waste.
What can you do? (spoiler: say what you mean)
So, I’ve gone through where I see the issues of using short-handed terms - but what actions can you take?
Stop using BIM Levels to specify the collaboration and technical requirements for information management. If you receive specifying documents stating this, challenge it. SAY WHAT YOU MEAN.
Use short-hand terms like 4D and 5D for broad discussion but don’t let that block further discussion and definition. SAY WHAT YOU MEAN.
Anything beyond 5D is poorly defined. Don’t use these terms at all. SAY WHAT YOU MEAN.
Both the appointing and appointed parties should set a baseline off ISO19650 for information management, using UK BIM Framework as guidance. Define and challenge information requirements early to try to mitigate the risk of taking poorly defined requirements into contract.
What do you think about the benefits and challenges of implementing IM? Have I missed anything? How can I improve my thinking? Please reach out in the comments 👇 on Twitter, or on LinkedIn.
It's a very ironic situation that the tool developed to give an unambiguous, scalable, full-life-cycle structured dataset to the industry has become bogged down in semantic misunderstandings, assumption and hearsay. We have work to do.
Great article.