published as: Stevens, G., Pipek, V. and Wulf, V. “Appropriation Infrastructure: Mediating appropriation and production work” in: Special Issue to End User Development in the Journal of Organizational and End User Computing, 22(2), p. 58-81 Appropriation Infrastructure: Mediating appropriation and production work Gunnar Stevens, Volkmar Pipek, and Volker Wulf University of Siegen and Fraunhofer FIT