How to Perform a Value Copy by Linking Nodes and How to Perform a Value Copy by Linking Nodes discussed how to use the drag and drop action to create a mapping between a source and target element or attribute. The drag and drop action creates an XPath expression in the XSLT that references specific nodes in the source document.

For example, the following XSLT code is generated by mapping a source element to a target element:

<ID>
 <xsl:value-of select="/ns0:PurchaseOrder/ID"/>
</ID>

The preceding code contains an xsl:value-of statement. The select attribute for this statement contains an XPath expression (/ns0:PurchaseOrder/ID)that references the source node being mapped.

This XPath expression represents a location path expression. XPath expressions can also be complex and include XPath functions and operators.

For example, the following code concatenates the value of the source element /PurchaseOrder/ID to the value of the attribute, /PurchaseOrder/@PONumber. It then assigns the result to the target element, <ID>.

<ID>
 <xsl:value-of select="concat(/ns0:PurchaseOrder/ID,/ns0:PurchaseOrder/@PONumber )"/>
</ID>

In the preceding code, the value in the select attribute is the XPath expression. The XPath expression uses the concat function to concatenate two source node values.

The XSLT Map Editor provides a number of ways to enter more complex XPath expressions than those that are created by simple drag and drop actions. The following methods for creating XPath expressions are available in both Map and XSLT View.