When using namespaces, it is important to remember that XPath matches qualified names
(QNames) based on the namespace URI, not on the prefix.
Therefore the XPath "//foo:bar" may not find a node named "foo:bar" if the prefix "foo" in the context of the node and in the execution context of the XPath are mapped to different URIs. Conversely, "//foo:bar" will find the node named "biz:bar", if "foo" in the execution context and "biz" in the node context are mapped to the same URI.