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The basic primitive for accessing a source document is the axis step. Axis steps may be combined into path expressions using the path operators "/" and "//", and they may be filtered using filter expressions in the same way as the result of any other expression.
An axis step has the basic form axis::node-test, and selects nodes on a given axis that satisfy the node-test. The axes available are:
element: age
element: age
The rest of the axes act in the same manner.