Available xpath functions

If you want to know the signature of a function, you can take a look at the xpath-functions.xml
This file can be found where your Application Server is installed. This has a list of all available functions and under which namespace each is registered.

For example on an MS Windows 2003 Server it could be C:\product\10.1.3.1\OracleAS\bpel\domains\default\ or under C:\product\10.1.3.4\OracleAS2\bpel\system\config