1. A graphical mapping interface for creating and displaying a schema map, wherein the graphical mapping interface is displayed on a screen and implemented with computer-readable instructions, which are stored on a non-transitory computer-readable storage medium and executed on a processor, and wherein the graphical mapping interface comprises: a main map window comprising a source schema region adapted for displaying a graphical representation of a primary source schema defining a structure of a primary data source; and a pop-up map window accessible from the main map window, wherein the pop-up map window comprises: a source schema region adapted for displaying a graphical representation of the primary source schema, wherein the primary source schema comprises at least one source node; a target schema region adapted for displaying a graphical representation of an intermediate target schema, wherein the intermediate target schema comprises at least one intermediate target node; an expression region adapted for displaying at least one target field expression for at least one intermediate target node displayed in the target schema region of the pop-up map window; a mapping region adapted for creating and displaying a graphical representation of one or more links connecting one or more nodes of the primary source schema to one or more nodes of the intermediate target schema within the pop-up map window; and wherein upon closing the pop-up map window, a graphical representation of the intermediate target schema is displayed in the source schema region of the main map window and accessible for mapping within the main map window.