In today's BIM world the "I" of information becomes more and more important. This information is driven mostly by the properties attached to an element, more than by it's geometry.

OBD already has a lot of built-in properties, also when it comes to quantities. Every type of element has their own set of quantities like NetArea, GrossArea, ...

But always some values are missing that could be of importance to the user. So we should be allowed to calculate our own values and assign them to the object as properties again. I can think of a lot of examples, when it comes to quantity takeoff:

• Twice the "Gross Side Area" for formwork of walls

• Volume multiplied with a certain factor (eg. 150 kg/m³) to estimate the amount of rebar

• Volume of spaces (which is area*height)

• ...

But also other things like the width of a door for example. There are at least 3 different width's that are important in a project: The door leaf width, the useful 'clearance' width and the width of the opening in the structural element. They are not always necessarily modelled in great detail. And even if they are it's important to be able to report these values.

Please give us the ability to add calculated values to the elements. Preferably from the DG catalog. See also this link on the forum where I try to approach this situation using Item Types (but currently failing).

What's important is that:

• Calculated properties are attached to the element (and not just a column in a schedule/report as it is in Revit)

• We can report these properties in OBD as well as export to Excel, CSV, ...

• Those properties can be exported to IFC and mapped according to user needs.