This class bridges PullProvider events to XMLStreamReader (Stax) events. That is, it acts as an XMLStreamReader, fetching the underlying data from a PullProvider.
A PullProvider may provide access to any XDM sequence, whereas an XMLStreamReader always reads a document. The conversion of a sequence to a document follows the rules for "normalizing" a sequence in the Serialization specification: for example, atomic values are converted into text nodes, with adjacent atomic values being space-separated.