Add to ORKGComputer-Aided Control System Design (CACSD) packages should be OPEN for (nonlinear) model and data import as well as export. In the following a low-level subroutine interface is proposed to define parameterized, event-driven, explizit ordinary differential equations or differential algebraic equations in form of input-output ''blocks''. A model which is described according to this interface definition is called DSblock (Dynamic System block). A DSblock may serve as neutral ''model bus'' to exchange nonlinear models between different modelling and simulation environments. The DSblock interface is designed to be able to describe models of multibody programs like SIMPACK, NEWEUL, DADS, electric circuits programs like SPICE, general purpose si...