Analyzing data in terms of relative position within time periods can be useful; for example, knowing that some costs increase in the last week of each quarter can help you balance expenditures. Linked attributes enable data analysis based on relative time periods such as the first month of a quarter, or the fourth week of a month.
Linked attribute dimensions can be associated only with the date-time dimension. Defining linked attribute dimensions is part of the Create Date-Time Dimensions wizard. The linked attribute dimensions that you create are based on the time depths you select when you define the calendar for the date-time dimension. For example, as shown in Figure 162, Sample Date-Time Dimension with Linked Attributes, if you select year, quarter, and month time depths and create linked attributes, the wizard creates three linked attribute dimensions (default dimension names): “Quarter by Year,” “Month by Year,” and “Month by Quarter.” Each attribute dimension contains members with sequential numeric names, indicating a relative position that will be used in analyzing the members associated with that attribute.
Linked attributes enable you to compare sales of the first month of a quarter against sales of the second and third months of a quarter in a simple crosstab analysis, as shown:
Note: | Linked attributes cannot be assigned to year time-depth members. |
Linked attribute dimensions reflect two time components, which are easier to understand if we use the default names; for example, “Quarter by Year.” Members of the “Quarter by Year” dimension are associated with quarter time-depth members such as “Quarter 1 of Gregorian Year 2008” in Figure 162, Sample Date-Time Dimension with Linked Attributes. The first time component, “Quarter,” is called the association level, because it indicates the date-time dimension members to which the attributes are associated.
The second time component in this example, “Year,” is called the attachment level. The attachment level indicates a member level in the associated date-time dimension. Each member of the linked attribute dimension contains a number that indicates a relationship between the association level and the attachment level. “Quarter by Year: 1” is the first attribute member “Quarter by Year: 2” is the second member, and so on.
The date-time dimension members associated with linked attribute “Quarter by Year: 1” are the first quarters of their respective years. All date-time dimension members with the attribute “Month by Quarter: 1” are the first months of their respective quarters. Thus linked attributes enable analysis of information based on a common periodic relationship such as first, second, and third.