In the traditional design process, plans and specifications created by the design teams did not impact the estimates created by the Quantity estimation teams because the information relevant to an estimate was just an overlay and not linked to the graphical representation. The surveyors would simply extract information from the documents passed on by the design team which would best suit their estimation requirements. But, in such a workflow, whenever there are any changes, it is impossible to keep track the differences between the drawings and estimates. Not to mention the inaccuracies in such a manual way of calculation.
However, in BIM the point of gathering and managing information begins right from the design model phase. The development of a 3D model is accompanied with the graphical representation of data-rich objects, the data being the product of the simultaneous Quantity Estimation. Each of these inserted objects are available in the future for the purpose of extracting relevant information by different project stakeholders. The nature of BIM compels us to manage information through all phases of a project.