In many applications, including Geographic Information Systems (GIS), it is necessary to interpret a given toponym mention as a particular entity in a geographical database or gazetteer.
the mention "Washington" in "He visited Washington last year" will need to be interpreted as a reference to either the city Washington, DC or the U.S. state of Washington, and "Berlin" in "Berlin is cold in the winter" could mean Berlin, New Hampshire or Berlin, Germany, among other possibilities.