3.3 Representations for describing
Representations are also used for specifying and communicating design details, to inform processes that lead to the realisation of an innovation. For example, the drawing in Figure 11c includes dimensional information which can be used to create a digital model of the site for analysis and evaluation. Such representations can be viewed as the output of the conceptual design process: a concept has been chosen, and some key parameters have been specified. At this point embodiment design commences, which involves evaluating and developing the concept against technical and economic criteria. This then leads to detailed design, which involves finalising details such as materials, dimensions, etc., so that the concept can be realised. Historically, drafting methods were used to compose detailed drawings of a concept. But, over recent decades computer-aided design (CAD) has replaced the draughtsperson. An example of a CAD model for a building design is illustrated in Figure 14a. CAD representations are powerful because they are defined as data that include formal information, implicit within the structure of the representation. Once a detailed model has been created it is possible to extract this data for use in embodiment processes, such as analysis and fabrication. The digitisation of representations makes it possible to carry out sophisticated numerical analysis for testing mechanical properties, or simulations for testing performance (The Economist, 2008). For example Figure 14b illustrates an analysis of the water subsystem of a building.