What happens if the context item value is the wrong type?
Do we allow the value to come from another implementation?
What happens if the variable value is the wrong type?
Do we allow the value to come from another implementation?
A way to serialize the query result
event api?
other data model node accessors (typed value, parent, attributes, children)?
accessor for the parts of an xs:QName ?
serialize a node
a way to concatenate two sequences?