Now, in order to convert input string to lowercase, below xPath function is available to do so-
Function: xp20:lower-case()

Problem Statement
After putting the input in above xPath function, the BPEL process compilation got failed with below error message-

“Error- namespace prefix xp20 can not be resolved”

JDeveloper– 12.1.3.0
SOA Suite– 12.1.3.0

Cause
In order to use any namespace specific operation, this must be included in your namespace declaration. If missing, generally throws error of namespace resolution i.e. this is something like we are trying to use a namespace prefix whose reference is not available. There might be scenario when the namespace declaration got deleted accidentally when working on source view of BPEL process.

Solution
Include below namespace declaration for xp20 prefix and corresponding transformation reference to be provided-

xmlns:xp20=”http://www.oracle.com/XSL/Transform/java/oracle.tip.pc.services.functions.Xpath20″

Now, recompile the SOA composite, this should compile successfully.

Reference(s)- Oracle Doc ID: 2182535.1, Bug ID: 23302378