exists in XI Message Mappings

Use

Use this function to determine whether a particular source field exists in the XML instance to be processed. If it does, exists() returns the value true, otherwise it returns the value false.

Example

In the example below, a function description is to be mapped to a structure that merely comprises the technical name and the description of the function. The source structure field descriptionis optional, however, the target structure field descriptionOfUse is mandatory ( minOccurs = 1).

Source Structure (Left) and Target Structure (Right)

Field Name	minOccurs	maxOccurs	Field Name	min- Occurs	max- Occurs
FunctionDeclMsg	1	1	FunctionHeadingMsg	1	1
name	1	1	technicalName	1	1
description	0	1	descriptionOfUse	1	1
inputArg	0	64
name (Attr)	1	1
type (Attr)	1	1
returnValue	0	1
type (Attr)	1	1

Using the exists()function and other Boolean functions you can output a specified string by default if the description-tag does not exist here. This ensures that the target field descriptionOfUse is always completed and is never empty.

Message Mapping Using exists()

Target Field Mapping	Value of Constant()
/FunctionHeadingMsg=/FunctionDeclMsg
/FunctionHeadingMsg/technicalName=/FunctionDeclMsg/name
/FunctionHeadingMsg/descriptionOfUse= if( Constant() , Not(exists(/FunctionDeclMsg/description)) , /FunctionDeclMsg/description )	(No description available)

The text description of the if standard function must be read as follows: if( true>,
,
false>).

Example

Source Instance	Result
encoding="UTF-8"?> myFunc type="String" name="arg1" /> type="String" name="arg2" /> type="String" name="arg3" />	encoding="UTF-8"?> xmlns:ns0="workshopDemo"> myFunc (No description available)