@inproceedings{FrankGrabmuellerHofstedtetal.2011, author = {Stephan Frank and Martin Grabm{\"u}ller and Petra Hofstedt and Andr{\´e} Metzner}, title = {Constraints, Predicates, Functions and a Turtle}, booktitle = {20. Workshop der GI-Fachgruppe "Programmiersprachen und Rechenkonzepte", 2003}, year = {2011}, }