MTT: Model Transformation Tools. MTT is a set of Model Transformation Tools based on bond graphs. MTT implements the theory to be found in the book ”Metamodelling: Bond Graphs and Dynamic Systems” by Peter Gawthrop and Lorcan Smith published by Prentice Hall in 1996 (ISBN 0-13-489824-9). It implements two features not discussed in that book: bicausal bond graphs and hierarchical bond graphs.