About Multi-Instance XQuery Expressions

This topic describes how to use the Mapping Rule editor, Mapping tab, Mapping subtab, Multi-Instance Expression subtab, XQuery subtab to write an expression that defines key mapping for a multi-instance structure. This field is displayed when you select the target of a data element-to-data element mapping and select the Advanced radio button in the Mapping Rule Item topic, if the target data element is a member of a multi-instance structure.

Context: The input document is a source order item.
Prolog: You can declare the order item namespace in the XQuery prolog. For example:
```
  declare namespace prop='http://oracle.communications.broadband';
```
Body: The XQuery body returns a key value that identifies a source order item instance.

The following example shows an XQuery expression that returns the concatenation of two source order item properties for the key value.

fn:concat(prop:areaCode, '-', prop:localNumber)