You can create a mapping specification with a source or multiple sources and no target during the initial phase of mapping specification development. The mapping specification is not valid and you cannot preview it or load the results of the mapping specification to the target. However, you can edit the mapping specification to configure the target and validate it.

You can create a mapping specification with two or more sources and a target. When you use multiple sources you must specify a join condition for the sources.

You can create a mapping specification that uses another mapping specification as a source. During incremental development of a mapping specification, you may need to configure complex filters and rules. You can create separate mapping specifications to break down the complex logic. You can add each mapping specification as a source to develop the logical flow.