What is the use of Rule files in Essbase?

• To ignore the fields that do not need to be Build and loaded into cube.
• To concatenate two or more fields to one.
• To add dynamic meta data to the outline.
• To remove the unnecessary records during load.
• To change the scaling of decimal numbers.
• To remove the header from the input files.
• To add aliases and update the member storage properties.
• To reject invalid data records.

and many more you can do with rule files.