Reference
1. Strengthening UML Collaboration Diagrams
by
State Transformations_
Reiko Heckel and
Stefan Sauer
University of Paderborn, Dept. of Mathematics
and Computer Science
D-33095 Paderborn, Germany
2. Formalizing the Specification of Graphical
Modeling Languages
Greg Nordstrom, Akos Ledeczi
TR #: ISIS-00-200
4. Graph-Grammars- An Introduction to the
Double-Pushout Approach
Alfio Martini,
Hartmut Ehrig & Daltro Nunes