A base mapping definition is a mapping definition that contains a set of field mappings that are common to other mapping definitions. You can use a base mapping definition to speed the mapping definition process by reusing it as the foundation for more specialized mapping definitions, saving you the time and effort of manually redefining the same field mappings for each mapping definition you create.
For example, if your defect and story issues share a number of fields in common (issue number, short description, and comments, for example), you could create a base mapping definition called
shared that specified those field mappings. You could then create the defect mapping definition and base it on the
shared mapping definition. The defect mapping definition would inherit issue number, short description, and comments field mappings. Then, you could add to the defect mapping definition additional field mappings that are relevant only to defect issues, such as
severity, for example.
You create a base mapping definition as you would any other mapping definition. See Creating a Mapping Definition for more information.