what is a rule file in essbase?

1. A rule file tells essbase what changes to make to the data source and outline during a data load or  a dimension build.
2. In essbase we will use rules to map data values to an essbase database or map dimensions and members to an essbase outline.
3. Rule files are stored with the extension .rul.
4. Rule files are used to define which build method to use during dimension build, how to transform data values before loading them as source file(because source file may not exactly be in the format that essbase understands)