Short Answer:Contrary to MBSE and tool-vendor Muddle-Driven Marketecture hype, the differences between the SysML and UML modeling languages are more
lightweight and
dialectical in nature than
heavyweight and
substantive. This should be expected since SysML was originally designed to be used by Systems Engineers collaborating with Software Engineers applying UML for software analysis and design, and SysML is defined as a modestly extended pragmatic subset of UML 2. (See
SysML FAQ: Can SysML and UML model elements be combined in the same model?)