Chapter 11 Time-variant data
One of the essences of the DW 2.0 environment is the relationship of data to time. Unlike other environments where there is no relationship between data and time, in the DW 2.0 environment all data—in one way or another—is relative to time.
Figure 11.1 shows that all data in DW 2.0 is relative to time.
This fact means that when you access any given unit of data, you need to know at what time the data is accurate. Some data will represent facts from 1995. Other data will represent information from January. And other data will represent data from this morning.
In DW 2.0 then, whether it is explicit or implicit, all data has a moment in time that depicts its accuracy and relevancy. ...