The System Dynamics library uses Jay Forrester's system dynamics methodology for modeling mass and information flows in continuous-time systems. This methodology has been, and still is, widely used in research within the social and life sciences. The library itself is designed as a low-level graphical library with an interface similar to that of block diagrams. Another feature of the System Dynamics library is that differential equations are hidden from the user by using terms like levels and rates instead of state variables and state derivatives.