id Function

Selects elements by their unique ID.

node-set id(object)

Remarks

When the argument is of type node-set, the result is the union of the result of applying id() to the string value of each of the nodes in the argument node-set.

When the argument is of any other type, it is converted to a string and then split into a white space–separated list of tokens (white space is any sequence of characters matching the production); the result is a node-set containing the elements in the same document as the context node that have a unique ID equal to any of the tokens in the list.

The following selects the element with unique ID foo,

id("foo")

The following selects the fifth para child of the element with unique ID foo,

id("foo")/child::para[position()=5]

See Also

XML Data Types Reference