Measures

A measure is a group of calculations that shares the same context. A measure consists of calculations for each source system, time period, and for each unique combination of dimension value.

Measures are typically numerical values computed from source systems and put into context with dimensions. You can configure measures by defining which calculations need to be computed, along with the context (dimensions) to which the calculations are related. Upon deployment, a measure is represented by a table in the datastore, which contains the calculated values along with references to the related dimensions. Each record in the measure table represents a time-slice (period) for which the calculated values are computed.

Typically measure tables are updated with time, adding records for every time-slice defined by time-slicing dimensions and the measure period. As such, measure tables are updated incrementally, from the time defined by the data collection start time.

Because measure records are described by a time-slice, a measure object must at least have one time context defined either by a measure period, and/or time-slicing dimensions.

You can configure a measure period, which allows the computation of the measure calculations at the specified period. For example, a measure object configured with a measure period of one hour stores calculations in the measure table for every hour since the data collection start.

You can also add one or more time-slicing dimensions to the context of a measure. These time-slicing can be used instead of a measure period. At run time, time periods defined by all time-slicing dimensions and by the measure period are all combined together to create smaller, contiguous time-slices by which measure calculations are computed.

For more information about specifying a measure period, see "Configuring a Measure Period".

You have to provide a refresh rate for the measure. The refresh rate recomputes calculations for the current time-slice and also verifies whether a new time-slice must be defined. The following are three scenarios when considering the refresh rate and the measure period:

• The refresh rate is smaller than the measure period or the time-slice.

  The measure is updated until a new measure period or time-slice is identified. Thereafter, a new measure value is calculated.

• The refresh rate is bigger than the measure period or the time-slice.

  The refresh rate verifies whether a new measure period or a time-slice is identified since the last refresh period. New measure values are calculated for the identified measure period and time-slices.

• The refresh rate is equal to the measure period or the time-slice.

  A new measure value is calculated at the identified measure period and time-slice.

  NOTE: The refresh rate just defines how often the calculation is executed. The above scenarios are only the result of the refresh execution and are not explicitly triggered.

In addition to the refresh rate, the Update Period defines how much data is updated in the measure table. For example, if you configure a Measure object with a refresh rate of 15 minutes and an update period of 1 hour, every 15 minutes, the BI Gateway services update the last hour of data in the measure table.