6. An integrated development environment (IDE) data processing system configured for extensible markup language (XML) path (XPATH) expression debugging, the system comprising: an IDE user interface presented in a memory of a computer; an XPATH expression model generator comprising program code enabled to produce an XPATH traversal tree (XTT) model for an XPATH input expression; and, an XPATH expression debugger comprising program code enabled to apply a respective sub-expression of a plurality of sub-expressions to a selected XML document corresponding to a selected node in the XTT model in the IDE user interface to compute a result set for the sub-expression; and if the result set does not isolate a point of failure in the XPATH input expression, recursively selecting another sub-expression and computing another result set for said another sub-expression until a point of failure in the XPATH input expression is isolated.
6. An integrated development environment (IDE) data processing system configured for extensible markup language (XML) path (XPATH) expression debugging, the system comprising: an IDE user interface presented in a memory of a computer; an XPATH expression model generator comprising program code enabled to produce an XPATH traversal tree (XTT) model for an XPATH input expression; and, an XPATH expression debugger comprising program code enabled to apply a respective sub-expression of a plurality of sub-expressions to a selected XML document corresponding to a selected node in the XTT model in the IDE user interface to compute a result set for the sub-expression; and if the result set does not isolate a point of failure in the XPATH input expression, recursively selecting another sub-expression and computing another result set for said another sub-expression until a point of failure in the XPATH input expression is isolated. 7. The system of claim 6 , wherein the IDE user interface is a user interface to an Eclipse framework implementation.