Proposed four years ago, SMILE has made minimal progress toward a full-fledged specification that System Dynamics software vendors can use to interchange models. This paper attempts to move the development of the standard one step further with a draft specification of both the language that needs to be interchanged (SMILE) and an XML format for that language (XMILE). Central to the success of this standard is the idea of three increasing levels of compliance, only the lowest level (interchange of equations) being required of all vendors.