1. A computer-implemented method for schema mapping and the transformation of data associated with first and second documents, the method comprising: displaying to a user, with a graphical user interface (GUI), layouts of the first and second documents simultaneously, the first and second documents having different data schemas and being instantiated with elements containing data values; acquiring, from the user, at least one association usable to map at least a first element of the first document to at least a second element of the second document, wherein each of the first and second elements contains layout data; and storing the association including the layout data corresponding to the first and second elements.