A sequence of more than one item is not allowed

Issue:

After creating a mapping activity that involves splitting, I'm encountering this error upon execution

2017-02-23 15:01:21 ; SystemID: ; Line#: 14; Column#: -1
2017-02-23 15:01:21 net.sf.saxon.trans.XPathException: A sequence of more than one item is not allowed as the first argument of saxonJavaMappingTransformation:processDateFormat() ("20170222...", "3", ...)

Cause:

Generally, this issue comes up when the Date Format function is being used in a mapping rule where a for each should be in place (on the parent node) but is not. This results in multiple date values being passed to the Date format function, instead of a single date value. Hence the error message
"A sequence of more than one item is not allowed..."

Solution:

To debug the issue, the quickest way would be to search the Mapping XSL for where the Date Format function is being used (i.e. processDateFormat from the error message).

Next, you can identify the incoming value(s) of the source data ("20170222...", "3", ...) then figure out what target field that data is mapped to per your business requirements.