The paper examines proposals for nD BIM with respect to what may be considered a dimension and how dimensions relate to information in a symbolic representation. It establishes that 'dimension' is often used metaphorically to indicate information-processing capacitiesan unfortunate usage in an area where the term is used literally. The paper proposes that a dimension in symbolic building representations should be a primary property of a symbol, not derivative, and moreover essential for the

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... tity of the symbolized object, i.e. not subject to abstraction. On the basis of these principles, it is reasoned that BIM can only be 4D.