Time, Product, Promotion and Store are the dimensions on which sales figure depend. The dimensions together are assumed to uniquely determine the measure. Each dimension is described by a set of attributes. The attributes of a dimension may be related via a hierarchy of relationships. The conceptual model for OLAP also lays stress on aggregation of measures by one or more dimensions as one of the key operations.
Time is a dimension that is of particular significance to decision support.
Later in this report I shall mention more about the manners in which we can make use of this dimension. In the Visual Display of Quantitative Information , Tufte explains that by displaying mortality data visually, Dr. John Snow was able to determine that a cholera outbreak in London was due to a contaminated public water well. He convinced the local city council to shut down the chief offending well. Mortalities promptly dropped. The important role which visualization plays in aiding the understanding of numerical data has been recognized for a long time.