XPath 2.0 builds on top of XPath 1.0 and adds much more power, including expressions like if , for , some , and others that we'll see in depth in the upcoming chapters.
Sequences are new in XPath 2.0, and they are ordered collections of zero or more items. And an item is either an atomic value or a node.
XPath 1.0 supported only four data types, XPath 2.0 extends that to support not only the node kinds supported in XPath 1.0, but also many atomic types, which include the primitive simple types defined by the XML Schema specification and values whose types are derived from them by restriction in a schema.
