In Chapter 8, we learned how to define atomic simple types. This chapter covers the other two varieties of simple types: union types and list types.
As we saw in Chapter 8, there are three varieties of simple types: atomic types, list types, and union types.
• Atomic types have values that are indivisible, such as
• List types have values that are whitespace-separated lists of atomic values, such as
<availableSizes>10 large 2</availableSizes>.
• Union types may have values that are either atomic values or list values. What differentiates them is that the set of valid values, or “value space,” for the type is the union of the value spaces of two or more other simple ...