The macro at-location informs the dspec system that the source for definitions done during the execution of body are at the location location .
location is usually a pathname, for definitions occuring in a file or editor buffer with that pathname.
Other locations are reserved for internal use. These are:
Defined in an editor buffer with no pathname.
Interactively defined.
Defined without dspec information being recorded.
An aggregate defined by the existence of a part.