Bond graphs are a network-like description of physical systems in terms of ideal physical processes. With the bond graph method we split up the system characteristics into an (imaginary) set of separate elements. Each element describes an idealized physical process. To facilitate drawing of bond graphs, the common elements are denoted by special symbols. This library contains all kind of bond graph elements. If you want to know more about modeling with bond graphs, please have a look at the modeling tutorial.
The standard library contains single dimensional bond graph elements. The 2d Library contains elements with multi-bonds of size 2 and the 3d library contains elements with multi-bonds of size 3.