SOI basics: Stages, Uses, LOD and Drop Points in light of BIM’s purpose

To better understand the set-of-information (SOI) approach to BIM data management I’m proposing, let’s review some key workflow notions in light of the purpose for which BIM exists.

The purpose of BIM, in my view, is “to give each actor just the information they need at just the right time throughout a building’s lifecycle – to support its effective design, creation and use.” An actor is any person, system or machine involved in a building’s lifecycle and component production.



Efficient delivery of information is needed “throughout a building’s lifecycle.” In other words, at every stage in a building project information relevant to that stage is needed. The AEC industry largely agrees on how to divide up the building lifecycle. I like the explanation of stages in the UK’s RIBA Plan of Work 2013. The big picture looks like this:

RIBA Plan of Work - STAGES


In order to give each actor in a BIM project “just the information they need,” it’s essential to know the BIM uses in which they’re engaged at the moment. Information needs vary greatly when using a BIM model for drawing production, for example, as opposed to using it for prefabrication, asset management, or something else. Here’s a categorization of the different BIM uses:



In defining how much detail (LOD) BIM actors need in the information they’re given, what’s of value is “the level of detailed geometry for a building component in its digital 3D graphical representation.” I use the acronym “GR” for that. Note that what an actor needs is not some general degree of detailedness for the BIM model as a whole, but a specific GR for each specific BIM object that’s relevant to that actor’s current BIM use.

We can categorize the GR of a building component as follows:

GR1 – 3D model of the BIM object with approximate dimensions

GR2 – 3D model of the BIM object with precise external shape dimensions

GR3 – 3D assembly of GR1/GR2 BIM objects

GR4 – 3D assembly of GR2 BIM objects for fabrication

Here are two examples of objects at these different GRs:




Precast Column
Precast Column


Giving information to actors “at just the right time” means identifying the specific times at which the delivery of specific information is needed. These information drop points should be defined with reference to the relevant project stage and BIM use. The category codes for stages and uses listed above can be used here.

I suggest the annotation format ~STAGE.BIM-USE.DROP-NUMBER.


For example:

Drop Point Description
~S2.DO.01 stage two / cost estimation / first drop
~S2.DO.02 stage two / cost estimation / second drop
~S3.DO.01 stage three / cost estimation / first drop
~S4.DE.__ stage four / scheduling / __ drop
~S7.DO.∞ stage seven / cost estimation / ∞ drop


With the above considerations and definitions, the following simple example of a set of information (SOI) should be easy to understand:

With that, with an SOI in other words, we are indeed providing a specific BIM actor with “just the information they need at just the right time.” Quite simple, really. And efficient.

In my next post I’ll examine the lifecycle of individual BIM objects – how the related information needs change as a building project advances.

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