Business process Systems Modeling Language tool. Astah SysML is a general-purpose graphical modeling language for specifying, analyzing, designing, and verifying complex systems that may include hardware, software, information, personnel, procedures and facilities. It helps engineer large, complex systems more safely. Every engineering specialty, from mechanical to electronic to software engineering have a common language to design safe, complex systems architectures. Astah SysML is a modeling tool that enables you to draw SysML diagrams swiftly with refined and intuitive interface design.