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Talk about information technology to construction professionals these days and the conversation will often quickly turn to building information modelling (BIM) - not least because of recent news that the UK government may make BIM mandatory across all public sector projects in the near future. But what exactly is BIM?

BIM is not new. The concept has been around since at least the 1980s - a time when many architects and engineers were making the transition from hand-drawn designs to computer-aided design (CAD) - and it can be useful to look at the history to understand what BIM is all about.

With the first CAD tools, hand drawings were replaced by digital 2-dimensional, 2D, versions, dramatically accelerating the process of editing design revisions. The subsequent advent of 3D design meant virtual models of the built asset could then be shown to clients, planners and fellow project team members.

As well as using them to produce conventional 2D drawings, designers could also use 3D tools to refine their designs and identify potential problems before construction started on site (for example, giving their customers virtual reality fly-throughs, using them for 鈥檆lash detection鈥�, and so on).

The next step was to complement the graphical representation of an object - a door, for example - with additional characteristics that, as well as that object鈥檚 physical shape and dimensions, provided details of its colour, cost, material, etc, and its functional relationship with other components.

As a result, such 鈥檖arametric鈥� design enabled the output not just of drawings and 3D representations, but also specifications, schedules, cost reports and other design, construction and - looking longer-term - operation and maintenance information.

BIM effectively adds other dimensions. First, the model can be used to model how the building will be constructed (time, so 4D); then you can associate cost data (5D), and then other aspects such as its energy use and sustainability credentials can be modelled. As a result, some commentators describe it as nD. The value of BIM also extends beyond design and construction, delivering information that an asset owner can use for facilities management, refurbishment or eventual demolition, for example.

And as more information is integrated into the model, so, too, should the professional inputs to the delivery of the asset. Traditionally different designers separately produced their own designs and associated information, but BIM offers a means for people to collaborate, to share and develop a single model. The whole asset can, in effect, be seamlessly constructed virtually, with everyone 鈥渨orking off the same hymn sheet鈥�. The , accordingly, stresses it is a 鈥渟hared knowledge resource鈥�:

鈥満诙瓷缜� Information Modelling is digital representation of physical and functional characteristics of a facility creating a shared knowledge resource for information about it forming a reliable basis for decisions during its life cycle, from earliest conception to demolition.鈥�

However, in some respects, BIM faces similar cultural, organisational and technological hurdles to those that often hamper the introduction of collaborative approaches. Owners, designers, contractors and supply chains need to be committed to the idea from the outset, and they need the appropriate knowledge, processes, tools and infrastructure to help them collaborate electronically.

IT vendors also need to enable easy exchange of data between the tools used by different team members ( is at the forefront of promoting such interoperability), and there will be challenges in managing the huge files often associated with complex BIM projects.