Will NBS’ newly-launched BIM Object Standard document help provide the confidence in downloadable content the AEC industry so desperately needs?
Downloadable Building Information Modelling (BIM) content is very welcome, especially when it reduces modelling time and comes loaded with useful information for downstream building and facilities management processes and supports industry standard formats like COBie. However, with so many people creating content, either for manufacturers or for in-house purposes, the quality and consistency of these objects varies hugely, making many experienced BIM users highly cautious of introducing externally created BIM content into managed models.
While there are many working groups developing standards to drive the UK Government’s BIM aims, the commercial BIM content market has to date escaped any policing. But the deliverables must ultimately comply with a number of industry standards including BS1192, PAS1192-2/3, RIBA’s Plan of Work, COBie-UK and BS 8541.
It is high time that commercial developers started to ensure their BIM content assists users, instead of very possibly creating geometry and information formatting problems up and downstream. NBS has created a documented ‘standard’ for its object library, which it hopes other firms will adopt.
NBS BIM Object Standard is a free downloadable PDF from its website. The standard is not a format, like IFC or DWG, but a written list of definitions and criteria that NBS has identified as being a baseline for consistency, efficiency and interoperability.
The 44 page document breaks down the five key areas that the standard addresses: General, Information, Geometry, Functional and Metadata. Properties are defined as ‘Shall’ (essential), ‘Shall not’ or ‘May’ (supplemental) this provides a baseline of essential information with some flexibility to include additional useful user defined data.
The General requirements cover categorisation, IFC object type and level of detail (LoD). For instance, BIM objects must be presented as ‘generic’ or manufacturer object, ‘component’ or ‘layered’ and assemblies of components must conform to BS 8541-3. The minimum will have a schematic LoD that must conform to BS 8541-3.
For object type identifiers, the standard invokes IFCtypeObject and IFC predefined type from buildingSmart IFC2x3. If objects do not have an appropriate IFC definition then user defined name convention guidelines are provided.
Information requirements cover general conventions, values, property groups and usages, data formatting, property naming, IFC property sets and COBie type and component properties, as well as some supplementary ‘when applicable’ but not essential information.
This section seeks to drive compliance with COBie version 2 Release 4 and IFC2x3 and PAS 16739 2005. It also shows how Revit has a property grouping convention outside of IFC, ArchiCAD, Vectorworks and AECOsim.
Geometry seeks to identify the minimum requirement to define the BIM component in shape, symbol, space, surface, material and connection, including dimensional and measurement basics. The first being: ‘The BIM object geometry and graphical detail shall not compromise the performance of the project model in which it is placed’.
This is great common sense, but how big is too big? Scales of 1:20. 1:50 and 1:100 are covered.
The Functional section is short and deals with a number of statements on embedded relationships, behaviours, constraints and connections.
Metadata addresses naming conventions for files, objects, properties, layers, materials and images within objects. Some obvious stuff here on no duplicate names, alphanumeric characters, spaces or punctuation.
The document is driven by common sense and is a good, broad guideline linking typical BIM Object structures to their relevant UK and International BIM standards. Some standard definitions areas are a bit vague, and act more as a guide and others, such as measurement units are only implied by the numbers (mm, cm, inches or mars bars!).
For a first attempt this is more comprehensive than I expected.
Conclusion
Defining BIM standards is tricky as it is the final deliverables that must conform. Here, NBS has worked with its major customers of downloadable BIM content, and launched with endorsements from an array of industry folk such as Autodesk, Bentley, buildingSMART, Graphisoft and Nemetschek.
The standard applies to its own NBS BIM library content but the competition, i.e. BIMobject, has not pledged to conform.
With NBS being part of RIBA and having a strong presence in the market, it perhaps could plausibly implement a de facto standard in the UK, but it would not be enforceable. One should not forget that the BIM object market is competitive and a ‘for profit’ business. Owning ‘the standard’ would undoubtedly be of commercial benefit.
That said, NBS has done a positive thing; it has taken action on a serious industry problem and has produced a BIM standard as a quality statement that means its BIM content will, in future, comply with key enforced industry deliverable standards. It is all about confidence in downloadable content. We will have to wait and see how far outside NBS’s circle of influence the standard is adopted.
While the UK, Netherlands, Denmark, Finland and Norway already require the use of BIM for publicly funded building projects, the EU will now adopt BIM by 2016. Suddenly, BIM software developers and building component manufacturers will have to contemplate supporting 27 more European BIM standards than just those that are developed in the UK.
■ nationalbimlibrary.com/nbs-bim-object-standard
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