XML Schema Complete Reference, The

10.8. The union Element

A simple type can specify a union of other simple types. The contents in the XML instance of an element constructed from a union can be any of the valid types. A union can be thought of as an “or” construct. That is, “a union b union c” is the conceptual representation of “a or b or c.”

Tip

A union may contain member types that have completely distinct base types, as demonstrated in Listing 10.8.

Listing 10.8 demonstrates the XML representation of the colorOptionType, which is a union of the anonymously declared standardColorOptionType, fancifulColorOptionType, and codedColorOptionType enumerations.

Listing 10.8. A union Specifying Local simpleType Elements (catalog.xsd)

<xsd:simpleType name="colorOptionType" id="catalog.colorOption.union.sType"> ...