CD-1 issue #4: generalized higher order functions

The issue number refers to the XLS-sheet found in this email:
http://lists.oasis-open.org/archives/xacml/200909/msg00013.html

The commenter finds that the higher order functions (any-of, all-of, 
etc) are not sufficient for his needs.

I do not understand from the comment what the more general higher order 
functions would look like. We would need a specific concrete proposal to 
consider to make progress.

Again, my personal preference is to move on what we have now. New 
functions are fairly easy to add in separate profile document since they 
do not affect the schema. So, I propose that we do not make any changes 
to the core, but we open up a new item of work with additional 
functions, and ask the commenter for proposals.

Best regards,
Erik