What’s classification got to do with it?


Nick Nisbet, Director at AEC3 Ltd and Technical Coordinator for buildingSMART UKI explores how classification is the key to the information and productivity revolution…

Classification is just a supplementary annotation. (Tina Turner, misheard.)

Draughting was so easy. I just added more and more lines and text till the drawing looked dense enough so the office supervisor stopped hassling me. Specifications and bills were judged by the number of pages.

Now I’ve been asked to use a BIM authoring tool, and the design manager has rejected my work because it lacks classification information. I have no idea what he wants from me, but I guess it’s going to slow me down: it already means I’m here late on a Friday evening. I know that when I joined the project we were told that we were following a new digital plan of work and the cost consultants were going to use BIM, but that’s for later, isn’t it? Not really.

Classification is the glue that join the objects in my BIM model to real assets in the real world. When I was using CAD I used named symbols (blocks, cells) and sometimes those symbols had strange names like A223-Column. Now I have a type (family, cell) library entry called CircularColumn – isn’t that good enough? Well, no and yes.

Unfortunately there is no agreement on the family names and, sorry, there never will be. The name of a Type is a flag to the human users, and at best it is specific to your region and discipline. It is only classification codes that connect to the real world. Yes, the Type should have a classification code embedded, but we need to check if it is one relevant to UK practice. Let’s also remember how we used to place symbols on layers – these layers included codes that were often different to the classification code in the symbol. How come? Well there are always two classifications for any object – one groups Products having similar intrinsic properties (its shape, colour, specification) and one groups Systems – things having a common purpose or function. Just like arranging your record collection by genre or artist, there is no right answer, but luckily Spotify and BIM lets me search by either and both.

Perhaps if your discipline is architecture then this distinction is lost on you: a window Component is a Type of window functioning as a window. A door Component is certainly a Type of door, but it may be functioning as part of the envelop system or it may be functioning as part of the internal divisions system. And when you hurriedly used the beam tool to model the brise-soleil sunscreen design, did you inadvertently get the wrong Type classification and the wrong System classification?

So setting and checking the Product Type classification and the function System classification pins down what you meant. The spec writer can use the first to refine the Type specification, and the cost consultant can use the second to generate the cost plan. Either role may also use the two classifications to elaborate their contribution. You may feel it is not your job to solve these problems, but let’s be honest, you are more likely to get it right than they are.

And remember that Digital Plan of Work? Is that their problem? No, it is yours because someone somewhere will check your model against the expected attributes for the current project stage, and if there is no classification information, or the wrong classification information, you will be marked down not just for not providing the contractually expected classification, but also by implication the contractually expected attribute information. It’s the classification code that joins your work to the digital check list.

OK, so you are used to those ANNN layer codes – we can carry on with them? No, because they only covered one half of the problem and were too focussed on domestic design and are obsolete – most people don’t even know their origin as CI/SfB. The door has closed on that era and it has closed on Uniclass1. Only Uniclass2015 is open for development and revisions. So get up to speed with table SS and table PR.

Why two tables? There cannot be one table that does both: a pump is one product but may have one of many functions, a wall has one function but may be created using many products. There aren’t three because we don’t do location/space-based costing, specification or subcontracting but we should make sure we model the spaces and locations and classify them to table SP.

Have I forgotten NRM1/3? No, we love it. But it lacks the coding rigour needed for use in BIM so I am happy that others say they can map Table SS to NRM. Have I forgotten NRM2 – well it did nearly slip my mind because NRM2 is open to using any table, PR, SS or even SP, but in practice it is used with actual or guessed contractor’s work breakdown structures – an approach that makes all Estimates, Tenders and Accounts awfully incomparable and incomparably awful.

So, reluctantly, we must learn to love classification, and get it into our BIM models and BIM product data. It is the key to the information and productivity revolution. ■

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Nicholas Nisbet

Director at AEC3 and Technical Coordinator buildingSMART UKI

Tel: +44 1494 714933





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