Summary and Aggregation
Base data is summarised and aggregated to provide a single source of performance measures. These measures are grouped by a number of categories, including, month, provider, purchaser, specialty, consultant and patient type.

Summarised and aggregated information is held at several "levels":

base data (detailed level data)
Internal groupings (for example Directorates for Trusts, or Providers for HAs)
External groupings.