This volume contains selected papers presented at the 12th International C- ference on Conceptual Structures, ICCS 2004, held in Huntsville Alabama, July 19-23, 2004. The main theme of the conference, "Conceptual Structures at Work," was chosen to express our intention of applying conceptual structures for hum- centered practical purposes. That invites us to develop not only clear conceptual theories, butalsomethodstosupporthumansintheapplicationofthesetheories in their societies. Some promising steps in this direction are being taken, but the gap between the researchers working on a highly...