An MMS file is a map source file created by Map Designer, which is a tool included with IBM Transformation Extender. It contains one or more maps in source format, which include input and output cards that define how to transform data objects from a source format to a target format.

To create an MMS file in Map Designer, select File → New → Map Source, choose the folder to save the map, name the map, and click Finish. MMS files must be compiled before they can be executed in Transformation Extender. Compiled map source files are saved as MMC files. IBM Transformation Extender is a program that allows users to integrate customer, business partner, and supplier transactions across an enterprise. Map Designer is used to develop maps, which provide input and output specifications for the transformation of data objects from the source format to the target format.