The type xs:IDREF
represents a cross-reference to an xs:ID
value. Like xs:ID
, it is most commonly used to describe attribute values. Each attribute of type xs:IDREF
must reference an ID in the same XML document. For example, the ref
attribute of the fnref
element in Example B-1 contains an xs:IDREF
value (again, assuming it is validated with a schema). Its value, fn1
, matches the value of the fnid
attribute of the fn
element. You can find all the xs:IDREF
values that refer to a specific ID using the idref
function.
Because xs:IDREF
is ultimately derived from xs:string
, xs:IDREF
values can be compared and used like strings. For more information on working with IDREFs, see "Working with IDs" in Chapter 20.
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