Structured Data in Revit

Further to my post about Universal Shared Parameters, we were questioned about why we needed such very structured data in our authoring environment. Why couldn’t we use the limited IFC properties available for our parameter names, or make do with IFC parameters that have TEXT or LABEL datatypes, or indeed use the Shared Parameters provided by National BIM Library. The answer is that if you want to unlock the true power of the data in BIM, the data has to be much better structured than those schemas accommodate.

Example 1 – IFC4 properties

Here is an example of how IFC4 handles Reaction to Fire (Surface Spread of Flame):

This entire definition consists of a property name, a data type, and a description (in several languages). The crudeness of referring to a nebulous ‘national building code’ is a good example of a bad starting point.

• Do we use BS or EN values?
• EN values are in 3 parts: class, smoke, droplets. How are they handled?
• Is this a limiting value, if so a max or a min?
• Is this a manufacturer’s value? How does it relate to the limiting value?
• Is this value certified, if so by which body?

It’s clear that if you really want to document Reaction to Fire of an element, you’re going to need a bunch of parameters, OR maybe fewer parameters from a schema that declares these criteria. Neither IFC nor NBL parameters are fit for this purpose.

 

Universal Shared Parameters

This post began not so much as a blog piece, but more a means of contributing to a discussion that isn’t limited to 140 character chunks…. (fix it Twitter!). I’m happy to be corrected / contradicted using the comments section, or back over on Twitter @pumphousebim

There is currently a healthy discussion on Twitter about the best way to resolve the ‘Shared Parameter Problem’. Although this is Revit terminology (and I will largely use Revit terminology throughout this post), this is part of a broader BIM discussion.

The problem is this – there is no universal list of Shared Parameters for the construction industry, either in the UK or worldwide. People may try and tell you otherwise, usually people who aren’t day-to-day Revit users – believing that COBie or IFC or National BIM Library (NBL – a UK body) offer a solution to this. They don’t.

This matters because – without Universal Shared Parameters, BIM in Revit doesn’t work very well. Conflicting lists of Shared Parameters, used by conflicting object publishers, cause massive problems for users and BIM Managers, problems which are passed on to Contractors, Subcontractors and Clients