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Hierarchy example

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A common example of a hierarchy is one which describes a method of grouping calendar dates.

It is often convenient to organise dates by calendar year. Information containing dates is often summarised in this way, so date hierarchies usually includes a set for each year covered by the data.

It is often useful to split each calendar year into four quarters, and within each quarter to group together those dates which lie in the same month. Most date dimensions therefore have a level containing a set for each quarter within the year sets, and a further level of month sets lying beneath.

Here is an example of how a date hierarchy could be designed. This conforms to the design of the MAST Crash Date Dimension.

ALL (Top level including every date in the list)

  • 2005 (Second level, grouping each year in the data together)
    • Q1 (Third level - grouping four quarters within each year)
      • Jan (Fourth level - three months within each quarter)
      • Feb
      • Mar
    • Q2
      • Apr
      • May
      • Jun
    • Q3
      • Jul
      • Aug
      • Sep
    • Q4
      • Oct
      • Nov
      • Dec
  • 2006
    • Q1
      • Jan
      • months as above
    • Q2
    • quarters as above
  • 2007
  • and so on
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