In this chapter, three semantics-based schema conversion methods are presented: 1) CPI converts an XML schema to a relational schema while preserving semantic constraints of the original XML schema, 2) NeT derives a nested structured XML schema from a flat relational schema by repeatedly applying the nest operator so that the resulting XML schema becomes hierarchical, and 3) CoT takes a relational schema as input, where multiple tables are interconnected through inclusion dependencies and generates an equivalent XML schema as output.