Implementations generally relate to extended schemas. In some implementations, a method includes displaying a first extensible markup language schema definition (XSD) schema, where the first XSD schema includes a plurality of XSD elements arranged in a tree structure. The method further includes receiving a selection of at least one XSD element of the plurality of XSD elements. The method further includes displaying one or more XSD extension selections associated with the at least one XSD element. The method further includes receiving at least one XSD extension selection of the one or more XSD extension selections. The method further includes appending in the tree structure at least one XSD extension element based on the at least one XSD extension selection.