A Solution Design Document (SDD) includes information about the working elements of the overall solution, including Dynamics AX standard features (Fits), Gaps, and integrations. It is important to get the entire solution depicted in a pictorial representation. The business process modeler in LCS is a great tool with which to put together the solution design document.
The details of the business flow in the future solution based on Microsoft Dynamics AX
The single point of reference for future value additions, issues, and troubleshooting
Documenting the high level
Business and solution flow diagrams