1. A computer-implemented method for drawing mapping lines between source and target objects, comprising: displaying a main view that shows one or more source objects, one or more target objects, and zero or more mappings between the one or more source objects and the one or more target objects, wherein a mapping line represents each mapping; receiving input that modifies the main view; and in response to receiving the input, sorting the mapping lines with a mapping strategy; and drawing the mapping lines based on the mapping strategy.